├── README.md └── LICENSE /README.md: -------------------------------------------------------------------------------- 1 | # Is Windows a joke [security analysis]? 2 | 3 | ![GitHub last commit](https://img.shields.io/github/last-commit/d3fenderz/windows_security?label=last%20update%3A) 4 | 5 | Is Windows a joke or are you? 🧢 6 | 7 | ## Report inaccuracies 8 | 9 | If you find something wrong or inaccurate, please [share your point of view](https://github.com/d3fenderz/windows_security/discussions/8). 10 | 11 | ## Windows is "inherently insecure"? 12 | 13 | I'm neither a Windows advocate nor a fan boy. [This issue](https://github.com/d3fenderz/windows_security/issues/7) is real. Still, there are ways to counterbalance/mitigate that, and other systems are not immune to similar attacks. 14 | 15 | If you're afraid of phishing campaigns and users clicking on tricked file types, then take the appropriate measures. 16 | 17 | ## General 18 | 19 | I'm probably not the only one to make jokes about Windows and its vulnerabilities. Indeed, Microsoft sells products to the vast majority of individuals, but organizations as well. 20 | 21 | A large range of businesses rely on Active Directories and other Microsoft technologies for their daily activities. 22 | 23 | Millions of users use these products every day. That's why it's a primary target for cybercriminals. 24 | 25 | While Windows' bad reputation was probably justified at a time, news versions seem particularly secure. It's just that Microsoft does not enable everything by default to appeal to the largest market share. 26 | 27 | ### Constructive Critics 28 | 29 | In 2022, I've seen multiple cases where Microsoft teams did not answer appropriately to major security alerts, ignoring security researchers and almost marking critical vulnerabilities as _won't fix_ or not answering at all. 30 | 31 | Specialists regularly complain about that. It's problematic as some flaws remain unpatched for weeks or months without remediation, sometimes without any mitigation. 32 | 33 | ### Windows vs. Linux vs. macOS 34 | 35 | If you compare with other OSes, Windows is secure. I'm definitely a Linux fan boy, but I can't recommend it to everyone, especially for security purposes. 36 | 37 | It shifts the responsibility to the end-users, exposing beginners and non-technical users to various risks, especially if you install alternative distros. A huge part of the global security is handled by browsers, not the system itself. 38 | You need to be a power user to leverage the benefits of Linux. While the latest versions are usually patched and way more usable, it's easy to completely mess up your configuration. 39 | 40 | At least, Windows simplifies the process and helps all users secure their machine (e.g., security patches, automatic updates, BIOS flashing, firmware updates). 41 | 42 | ### What you will find here 43 | 44 | I'm writing this guide to help you understand Windows and its security mechanisms. You'll also get helpful links to dig further. We'll see how to harden your configuration and activate interesting options. 45 | 46 | We'll see practical examples that help defending your system against common exploits. 47 | 48 | ### But security tools and policies can be disabled! 49 | 50 | Yes, and it's undeniably a good point. Many attacks attempt to modify registry entries to disable security tools and mechanims, allowing malware to spread and infect the entire system. 51 | 52 | Attackers can also leverage [LOTL attacks](https://encyclopedia.kaspersky.com/glossary/lotl-living-off-the-land/), using legitimate software to bypass detection. 53 | 54 | ### Static analysis is not enough 55 | 56 | Attacks can be identified by static analysis and signature-based detection. It's necessary but no longer sufficient. 57 | 58 | During forensic investigations and malware analysis, you may upload binaries or `.dll` to VirusTotal, but such static analysis on suspicious files won't help you with malicious instructions in memory. 59 | In many cases, defenders need dynamic analysis too, like behavioral detection, as built-in commands and mechanisms can be used to download poison from external IPs to install malware. 60 | 61 | Windows cannot prevent users from installing third-party applications by default, which is often the path used by cybercriminals compromise their victims. 62 | 63 | ### So, Windows is perfect? 64 | 65 | Nope. Don't get me wrong with this guide. My point is that it's probably less shitty than you and I think. Besides, your family and friends won't switch to Tails (even macOS) tomorrow. 66 | 67 | ## Basics of security on Windows 68 | 69 | ### 7 recommentations for the individuals 70 | 71 | My shortlist, no bullshit: 72 | 73 | * Enable Windows built-in security (Defender, Firewall, etc). 74 | * Keep the system and the applications up-to-date: download and install **all** patches available. 75 | * Keep the BIOS and the firmware up-to-date. 76 | * Encrypt the hard drive with [BitLocker](https://learn.microsoft.com/en-us/windows/security/information-protection/bitlocker/bitlocker-overview). 77 | * Connecting with Microsoft accounts is only useful to enable [Windows Hello](https://learn.microsoft.com/en-us/windows-hardware/design/device-experiences/windows-hello). Otherwise, use local accounts only. 78 | * Apply the least privilege principle: not all users need admin privileges (even you don't need to be admin all the time, so maybe create a standard account for daily activities) 79 | * As admin, define local security policies (e.g., strong password policy), apply mitigations, and sync files to make regular backups (e.g., have a clear recovery strategy). 80 | 81 | It does not mean you get a digital fortress after that, but it's not trivial to hack and usually requires social engineering and more sophisticated scenarios to make people install crap. 82 | 83 | ### About Windows 11 84 | 85 | Windows has better default policies and settings. 86 | 87 | If your machine meets the following requirements (you can use [health check](https://support.microsoft.com/en-us/windows/how-to-check-if-your-device-meets-windows-11-system-requirements-after-changing-device-hardware-f3bc0aeb-6884-41a1-ab57-88258df6812b) to verify it): 88 | 89 | * TPM 2.0 90 | * Security boot Enabled 91 | * DEP (Data Execution Prevention) 92 | * UEFI MAT 93 | 94 | It's recommended to switch to Windows 11. The latest version of the OS (at the time of writing) enables interesting features by default, such as Memory integrity, which protects the core from various hijacks and memory corruptions. 95 | 96 | The requirements also provide [zero trust protection](https://www.ibm.com/topics/zero-trust) out of the box. More pragmatically, such configuration eliminates _de facto_ entire classes of threats. 97 | 98 | A big caveat is that many people will attempt to bypass system requirements, trying to upgrade old machines to Windows 11, which is a very bad move, as it's not meant for that by definition, and you may lose both the security benefits and the usability (e.g., hardware performances). Many advanced security features, like [VBS](https://learn.microsoft.com/en-us/windows/security/threat-protection/device-guard/enable-virtualization-based-protection-of-code-integrity) are available on Windows 10 too. 99 | 100 | **Windows 10 will be maintained until Oct. 14, 2025** 101 | 102 | ### 7 Recommendations for the admins (businesses, organizations) 103 | 104 | It's hard to provide a generic list, as there are many configurations and products (e.g., Windows Server), but let's keep it simple: 105 | 106 | * Keep the system up-to-date, including the BIOS and the firmware, but also applications 107 | * Encrypt hard drives with [BitLocker](https://learn.microsoft.com/en-us/windows/security/information-protection/bitlocker/bitlocker-overview). 108 | * Consider suites like Windows 365 that provides recommendations for admins and advanced endpoint protection (there are many credible alternatives, but cloud-based security can be rewarding) 109 | * Apply the least privilege principle [see documentation](https://learn.microsoft.com/en-us/azure/active-directory/develop/secure-least-privileged-access) 110 | * Don't trust the default settings: define security policies (e.g., strong password policy), apply mitigations (e.g, Group Policies, additional kernel protection), and have a proper recovery strategy (tested) 111 | * Log sensitive [Powershell](https://learn.microsoft.com/en-us/powershell/) commands (e.g., Invoke-WebRequest, Get-FileHash) 112 | * Monitor endpoints, network traffic, and unusual activities (e.g., SIEMs, behavioral analysis, packets sniffers, event logs) 113 | 114 | ### Most bypasses involve initial access and malicious TCP connections 115 | 116 | Most demos that bypass Windows security need initial access before, but that's not the most complicated part. Phishing attacks are more and more sophisticated these days, so it's not uncommon employees get tricked into deploying RATs and other "connect-back" tools, especially when the company has no security culture. 117 | 118 | However, what bypasses Windows Defender is usually obfuscated powershell commands that start reverse shells and other malicious TCP connections. While it definitely works, any system would be fooled unless you monitor/filter packets and outgoing connections correctly, even on a fully-patched Windows (not a valid demonstration to me). 119 | 120 | Besides, cybercriminals often use legitimate platforms as "C&C" servers to bypass detection tools that focus on blacklisted domains and IP ranges. 121 | 122 | ### The System32 123 | 124 | You can read [this blog post](https://jmau111.github.io/2022/11/25/windows-system32-forensics/) for a quick introduction to essential concepts. 125 | 126 | `C:\Windows\System32` is the heart of the system. It contains all system configurations, settings, and binaries. If you or something else (e.g., a virus) damages this folder, you can say good bye to your environmment (regular backups are strongly recommended). 127 | 128 | That's why Windows does not let you destroy this folder and locks most files within, even for admins. 129 | 130 | Cybercriminals use it all the time, for example, to hijack `.dll` and or replace system binaries with evil executables. 131 | 132 | ### Active directory vs. LDAP 133 | 134 | Also known as AD, it's a Windows service that stores data objects, which can be users, devices, applications, or groups. Enterprises often use it to allow users to authenticate and manage various resources. It requires Windows Professional or Windows Enterprise, at least, but you usually test it with Windows Server editions. 135 | 136 | Attackers have multiple angles to attack, but they will likely target the domain controller, which is like a central computer (a server) that manages all other computers, devices and users (credentials) in the AD. 137 | 138 | It's essential to monitor events and attribute the right permissions (admins must fine tune access rights and controls) to keep the AD secure. For example, pen-testers like to perform password spraying and other malicious attacks on such service. 139 | 140 | Admins can enable features like Security auditing to monitor success and failures. They can also track operations like synchronizations, backups, or migrations. 141 | 142 | LDAP means "Lightweight Directory Access Protocol" and is designed for enterprises. It provides a pretty convenient set of commands to query information. Active Directory can implement this protocol to allow interactions with LDAP-based applications. 143 | 144 | There are various enumerations and attacks that pen-testers can perform to extract sensitive information from crafted LDAP requests, so admin must ensure it's correctly configured. 145 | 146 | ## The Windows Registry 147 | 148 | ### In short 149 | 150 | > Registry files are located C:\Windows\System32\Config and contain keys and associated values that control critical functions. For example, UAC (User Account Control) can be deactivated by modifying the value of a specific key in the Windows Registry. 151 | 152 | [Source: A quick Journey In The System32](https://jmau111.github.io/2022/11/25/windows-system32-forensics/#basic-forensics) 153 | 154 | **It's essential to backup registry entries before any modification**, as the system continually references them during its operations. 155 | 156 | The Registry is one of the most critical areas to protect and monitor, as `reg query` commands allows reading and modifying pretty much everything on the system, including security settings. Using a group policy (gpedit.msc > user configuration > system: "prevent access to the registry editing tools") or the Registry itself, you can restrict its access. 157 | 158 | It's not the ultimate protection, but it's still an additional layer. 159 | 160 | You can use software like [regshot](https://sourceforge.net/projects/regshot/) to take snapshots of the Registry. It's useful to restore the system when it gets unstable, and also valuable for forensic analysis. 161 | 162 | ### What are the hives? 163 | 164 | > A registry hive is a group of keys, subkeys, and values in the registry that has a set of supporting files that contain backups of its data 165 | 166 | Most hives[^1] begin with "HKEY" and are on the top of the tree (~ hierarchy). You may find the term "root keys" instead, but it's the same thing. If you open the Registry editor, you'll see the following virtual folders: 167 | 168 | * `HKEY_CLASSES_ROOT`: data for applications 169 | * `HKEY_CURRENT_USER`: personal settings of the current logged-in user 170 | * `HKEY_LOCAL_MACHINE`: system settings 171 | * `HKEY_USERS`: settings of all users 172 | * `HKEY_CURRENT_CONFIG`: hardware, drivers 173 | 174 | The system does not let you modify their names or locations, as it considers there's no valid reason for that. Inside, you'll find various keys that control different functionalities, system settings, or users' preferences. 175 | 176 | The values associated to the keys can be `1` or `O` to enable/disable features but also strings like paths for system binaries. 177 | 178 | _N.B.: The editor represents the Registry as a **hierarchical tree**, but it does not reflect their actual locations on the disk._ 179 | 180 | ### Typical Windows commands 181 | 182 | Classic attacks often involve `reg query` commands to enumerate specific software (e.g., remote access tools), extract sensitive information, and even modify entries (e.g., abusing ImagePath to point to malicious executables). 183 | 184 | [Source: reg query - Microsoft](https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/reg-query) 185 | 186 | Of course, you can also open the Registry editor by typing "regedit" in the search bar, but it usually requires admin privileges. 187 | 188 | More sophisticated attacks can store instructions for malware in registry entries, which allows evading signature-based detection. This can happen after a phishing attack or on a malicious website that leverages JavaScript to trick users into modifying their system. 189 | 190 | The ultimate goal is usually to gain persistence, as some hives and keys control the startup (e.g., HKEY_LOCAL_MACHINE). 191 | 192 | ### How to protect the Registry 193 | 194 | There are several ways: 195 | 196 | * backup entries regularly (e.g., manual backups, scheduled tasks, regshot) 197 | * monitor registry editing (again, regshot can help you compare 2 snapshots, for example, with the "compare" button) 198 | * whitelist allowed software 199 | * restrict access to the editor (e.g., using a registry entry or a group policy) 200 | * define local group policies to lock keys 201 | * program `reg query` commands to reset keys on startup 202 | * stop using software like ccleaner that can mess up everything (it allows the user to delete keys) 203 | 204 | ### Practical example: reverse shell 205 | 206 | ``` 207 | reg add "HKLM\SYSTEM\CurrentControlSet\services\regsvc" /t REG_EXPAND_SZ /v ImagePath /d "C:Temp\reverse_shell.exe" /f 208 | ``` 209 | 210 | The above command is a typical attack that attempts to abuse the ImagePath of a system binary to replace it with a malicious one and execute the reverse shell with higher privileges. 211 | 212 | The attacker only has to restart the service to make changes effective. 213 | 214 | It relies on weak permissions for Registry hives that allows users to modify keys for system components, which can ultimately lead to privilege escalation. 215 | 216 | ## Windows Mitigations 217 | 218 | ### Intro 219 | 220 | Windows 10 allows configuring additional security measures to mitigate common threats. 221 | 222 | For example, Pass-the-Hash or Pass-the-Ticket attacks can be mitigated by virtualization-based security (VBS) and Credential Guard in Enterprise and Server editions. Such attacks are massively used by attackers. 223 | 224 | Many CTFs emulate that, but it's not possible, or, at least, extremely hard with such mitigations. 225 | 226 | [Source: Windows documentation - mitigate threats](https://learn.microsoft.com/en-us/windows/security/threat-protection/overview-of-threat-mitigations-in-windows-10) 227 | 228 | ### Mitigation vs. remediation 229 | 230 | Both terms are part of risk assessment, but it's not the same concept. Remediation closes security holes and is the best option, but it's not always possible. While mitigations won't address the vulnerabilities, it can buy some time, reducing the likelihood of security flaws being exploited. 231 | 232 | ### Misknown security features 233 | 234 | [Specific functionalities](https://learn.microsoft.com/en-us/windows/security/threat-protection/overview-of-threat-mitigations-in-windows-10#table-3-windows-10-mitigations-to-protect-against-memory-exploits--no-configuration-needed) help mitigate common threats such as memory heap or pool memory exploits. 235 | 236 | You can also protect processes from tampering attacks. These mitigations remain quite misknown by most users, admins and developers. If correctly set, it can reduce the attack surface dramatically and contain infections. 237 | 238 | Other features include defenses against bootkits, rootkits, fake drivers, viruses and various malware. While this will certainly not stop everything, it can slow down adversaries, at the very least. 239 | 240 | ### Exploit guard and other mitigation controls 241 | 242 | [Exploit Guard](https://learn.microsoft.com/en-us/mem/configmgr/protect/deploy-use/create-deploy-exploit-guard-policy) is the successor to EMET (The Enhanced Mitigation Experience Toolkit) and provides core isolation and advanced kernel protection. Defenders can leverage it to enforce Windows 10 security significantly. 243 | 244 | Again, it's not available on all editions, but in a corporate context, it's highly recommended. Some overflows, race conditions, and logic bugs can be mitigated when your turn on core isolation. 245 | 246 | As you may already know, the kernel is the head of the system. Everything that runs at that level will have full permissions. That's why it's so important to isolate processes and prevent nasty leaks. 247 | 248 | ## Security policies 249 | 250 | ### Introduction 251 | 252 | Windows allows you to set [security policies](https://learn.microsoft.com/en-us/windows/security/threat-protection/security-policy-settings/how-to-configure-security-policy-settings) on the local device, on a domain-joined device, and on a domain controller. 253 | 254 | Many pre-defined policies are set to "no configuration" by default, but you can change the value and significantly harden your configuration. Just type `secpol.msc` on the start screen. You can also use `gpedit.msc` to modify local group policies. For example, you can use it to force strong passwords for all users. 255 | 256 | On Windows 11, you can also type "Local Security Policy" in the search bar. Indeed, there are multiple ways to open the editor. 257 | 258 | ### Pros and cons 259 | 260 | In my experience, Local Security Policy provides an interesting granularity, but it can be overwhelming at the beginning, as there are tons of rules, and labels are not always easy to understand. 261 | 262 | Besides, as it's a policy, it can be modified, for example, using Powershell commands to retrieve policies as objects. However, it's not a valid reason to skip such configuration, as you can restrict what users can do significantly. 263 | 264 | The good news is you can export/import policies as Windows allows you to save them as `.inf` files. 265 | 266 | ### A Misknown feature 267 | 268 | The vast majority of Windows users, including admins, rely on default policies. However, Windows does not enable many security mechanisms by default ( Windows 11 has a better default strategy, though), which extends the attack surface. 269 | 270 | It can prevent some risky behaviors and force good security hygiene. 271 | 272 | ### Practical examples 273 | 274 | Here are a few examples of security rules you can set: 275 | 276 | * Disable guest accounts: such accounts are not password-protected, so if you don't need them, set the corresponding policy 277 | * Set password expiration age: force users to renew their passwords regularly 278 | * Set minimum passwords length: secure passwords use various chars, lowercases, uppercases, and numbers, but length is even more critical 279 | * Disable Anonymous SID Enumeration: if you don't need that, just drop the functionality, as hackers will likely try to exploit it 280 | * Prohibit User Install: you can prevent users from installing third-party software 281 | 282 | ### Monitor changes 283 | 284 | I do not recommend building custom Powershell scripts to monitor GPO changes unless you master your art. Instead, many editions and cloud-based configurations allow you to be alerted of such changes automatically. 285 | 286 | It's strongly recommended for AD (Active Directory). 287 | 288 | ## Mitigate privilege escalations 289 | 290 | ### A short definition 291 | 292 | Privilege escalation consists of gaining unauthorized privileged access into a system, for example, by hacking an account with high privileges or by elevating the privileges of a classic account. 293 | 294 | You may also read the terms "horizontal" and "vertical." The first one refers to classic attacks when attackers impersonate users with similar access level or steal sessions (e.g.: XSS, CSRF). The term "vertical" is used to describe an **elevation**, a.k.a. when you get higher privileges (e.g., root). 295 | 296 | ### Obvious recommendations 297 | 298 | It might look obvious, but the following _reco_ are helpful: 299 | 300 | * don't give admin privileges to non-admin roles (least privilege principle) 301 | * don't rely on out-of-the-box roles and default permissions (yes, there's a risk of misconfiguration) 302 | * update and patch all the things: users may use Windows Update and applications' automatic updates or package managers such as [chocolatey](https://chocolatey.org/). 303 | * disallow unused protocols and remove remote access tools when it's not needed 304 | * disable services with unquoted service paths 305 | * use password manager or PAM (Privileged Access Management) solutions 306 | * force MFA for **all** accounts (e.g., AD, Cloud) 307 | 308 | ### Don't focus on the tools 309 | 310 | Many evasion techniques can be used to fool signature-based detection. It's better to put your attention on the results and the behaviors rather than the attacking tools. 311 | 312 | Enabling Credential Guard can mitigate credentials thefts seriously. Even if attackers manage to hide evil binaries such as Mimikatz, which is documented, enabling that _fabulous_ `SeDebugPrivilege` capability becomes challenging. 313 | 314 | ### Remove orphaned and guest accounts 315 | 316 | It's not uncommon for attackers to exploit orphaned accounts, especially in Active Directory. Such "ghosts" can be used as a point of entry, as the likelihood of weak password, disabled 2FA/MFA, or default settings tend to increase, and you won't see it coming. 317 | 318 | Unless you're a public platform, there's no reason to keep old accounts you may have created "temporarily" for a short period. It's the same with guest accounts that do no require passwords. The scope for such features seems pretty limited. 319 | 320 | ### Restrict Powershell, don't kill it 321 | 322 | Of course, you could disable it completely, but such radical measure usually creates more problems than it solves. Besides, Powershell commands can actually help forensics and incident response. Administrators also use it to automate security tasks. 323 | 324 | You can start with a group policy, so non-admin users cannot start the Powershell interpreter. There are documented ways to bypass such restrictions (e.g., [PowerShdll](https://github.com/p3nt4/PowerShdll)), but it's still a good layer to add. 325 | 326 | Another approach can consist of whitelisting specific PowerShell scripts only to mitigate the risks. You can reject unsigned scripts and restricting script execution. 327 | 328 | Admins must disable and uninstall any deprecated version of Powershell to mitigate abuses like that: 329 | 330 | ``` 331 | PowerShell -Version 2 332 | ``` 333 | 334 | Or classic downgrade attacks and injections powered by [unicorn](https://github.com/trustedsec/unicorn). 335 | 336 | Don't forget PowerShell has advanced logging capabilities to record and monitor sensitive commands, like `Invoke`. 337 | 338 | [Read the cheat sheet](https://github.com/d3fenderz/powershell_commands) to learn PowerShell attacks and effective defense mechanisms. 339 | 340 | ### Even more mitigations 🔒 341 | 342 | Some situations are more tricky for attackers: 343 | 344 | * if app developers use fully qualified path when loading DLLs 345 | * if admins change the ACLs of the folder when system privileges are required 346 | * if admins remove the path entry from the SYSTEM path variable when it's not needed 347 | * if only authorized admins can interact with service changes and target path locations 348 | * if file execution is disabled in user directories (e.g., downloads, tmp) 349 | * if `AlwaysInstallElevated` policy is set to disabled [^2] (as you woud expect by default) 350 | * if standard users do no have write permissions in the Registry (policy) 351 | 352 | [Source: Microsoft - Dynamic-Link Security](https://learn.microsoft.com/en-us/windows/win32/dlls/dynamic-link-library-security?redirectedfrom=MSDN) 353 | 354 | ## Additional tools for casual users 355 | 356 | These two softs are credible alternatives (at least, to me) to the built-in firewall and can even improve your privacy: 357 | 358 | * [simplewall](https://github.com/henrypp/simplewall) 359 | * [tinywall](https://tinywall.pados.hu/download.php) 360 | 361 | ## Best resources 362 | 363 | * [Attacking AD](https://zer1t0.gitlab.io/posts/attacking_ad/) 364 | * [PayloadsAllTheThings - Windows](https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/Methodology%20and%20Resources/Windows%20-%20Privilege%20Escalation.md) 365 | * [Windows Privesc resources](https://www.willchatham.com/security/windows-privilege-escalation-privesc-resources/) 366 | * [PowerShell loves the Blue Team](https://devblogs.microsoft.com/powershell/powershell-the-blue-team/) 367 | * [Fuzzy Security - Windows Privesc](https://fuzzysecurity.com/tutorials/16.html) 368 | * [Windows local privilege escalation](https://book.hacktricks.xyz/windows-hardening/windows-local-privilege-escalation) 369 | * [Windows Defender review 2022](https://www.comparitech.com/antivirus/reviews/windows-defender-review/) 370 | 371 | [^1]: the term "hive" is supposedly a dev's joke (easter egg), as one of the developers hated bees 372 | 373 | [^2]: it's no uncommon to find the value set to `1` in [vulnerable] machines configured for CTFs, but if your machine has the same configuration, it's a massive risk. 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Such new versions will 567 | be similar in spirit to the present version, but may differ in detail to 568 | address new problems or concerns. 569 | 570 | Each version is given a distinguishing version number. If the 571 | Program specifies that a certain numbered version of the GNU General 572 | Public License "or any later version" applies to it, you have the 573 | option of following the terms and conditions either of that numbered 574 | version or of any later version published by the Free Software 575 | Foundation. If the Program does not specify a version number of the 576 | GNU General Public License, you may choose any version ever published 577 | by the Free Software Foundation. 578 | 579 | If the Program specifies that a proxy can decide which future 580 | versions of the GNU General Public License can be used, that proxy's 581 | public statement of acceptance of a version permanently authorizes you 582 | to choose that version for the Program. 583 | 584 | Later license versions may give you additional or different 585 | permissions. However, no additional obligations are imposed on any 586 | author or copyright holder as a result of your choosing to follow a 587 | later version. 588 | 589 | 15. Disclaimer of Warranty. 590 | 591 | THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY 592 | APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT 593 | HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY 594 | OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, 595 | THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 596 | PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM 597 | IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF 598 | ALL NECESSARY SERVICING, REPAIR OR CORRECTION. 599 | 600 | 16. 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Interpretation of Sections 15 and 16. 613 | 614 | If the disclaimer of warranty and limitation of liability provided 615 | above cannot be given local legal effect according to their terms, 616 | reviewing courts shall apply local law that most closely approximates 617 | an absolute waiver of all civil liability in connection with the 618 | Program, unless a warranty or assumption of liability accompanies a 619 | copy of the Program in return for a fee. 620 | 621 | END OF TERMS AND CONDITIONS 622 | 623 | How to Apply These Terms to Your New Programs 624 | 625 | If you develop a new program, and you want it to be of the greatest 626 | possible use to the public, the best way to achieve this is to make it 627 | free software which everyone can redistribute and change under these terms. 628 | 629 | To do so, attach the following notices to the program. It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | --------------------------------------------------------------------------------