Fact Check: Are gz files safe?

Are GZ Files Safe?

The claim regarding the safety of GZ files revolves around concerns about their potential to harbor malware or be misused in cyberattacks. GZ files, which are compressed files created using the Gzip compression utility, are widely used for various purposes, including software distribution and data storage. However, as with any file type, the safety of GZ files can be compromised if they are manipulated or disguised by malicious actors.

What We Know

1. Gzip Vulnerabilities: There is a known vulnerability associated with Gzip, tracked as CVE-2022-1271. This vulnerability, while serious, specifically affects the zgrep command used for searching within Gzip archives, rather than the Gzip format itself. The implications of this vulnerability are limited, but it highlights that software can have flaws that may be exploited under certain conditions 3.

2. Malware Disguised as GZ Files: Security experts have reported instances where malicious files are disguised as GZ files. For example, a blog post from IronScales discusses how threat actors have been using CAB files renamed as GZ files to bypass security measures, allowing malware to execute on Windows systems without raising alarms 6. This indicates that while the GZ format itself may not be inherently dangerous, the way files are presented can lead to security risks.

3. Rising Popularity in Malware Campaigns: According to a report by TechRadar, GZ files have seen increased usage in malware campaigns, alongside other archive formats like ZIP and RAR. This trend suggests that cybercriminals are leveraging various file types, including GZ, to deliver malicious payloads 8.

4. General Security Practices: Security best practices recommend caution when opening any files from untrusted sources, including GZ files. A discussion on SuperUser emphasizes that while inspecting a tar.gz file is generally safe, it is crucial to avoid executing or opening files from unknown or untrusted origins 9.

5. File Type Confusion: A blog post on Security Boulevard warns users about the potential for confusion between file types, noting that a file labeled as .gz could be a different archive format altogether, such as .cab. This kind of deception can lead to unintentional execution of malicious software 4.

Analysis

The safety of GZ files cannot be assessed in isolation; it is influenced by various factors, including the source of the file, the context in which it is used, and the potential for manipulation by malicious actors.

• Source Reliability: The sources cited vary in credibility. For instance, the CISA advisories 12 are authoritative and provide well-researched information about cybersecurity threats. In contrast, blog posts from companies like IronScales and Security Boulevard, while informative, may carry a bias towards promoting their cybersecurity solutions. Therefore, while they provide valuable insights, they should be evaluated with caution.

• Conflicts of Interest: Some sources, particularly those from cybersecurity firms, may have a vested interest in portraying certain file types as dangerous to promote their security products. This potential bias should be considered when interpreting their findings.

• Methodology Concerns: Many claims regarding the safety of file types rely on anecdotal evidence or specific case studies rather than comprehensive statistical analysis. For example, while the increase in GZ file usage in malware campaigns is noted, the exact mechanisms and prevalence of such incidents require further empirical research to substantiate claims about their safety.

• Need for Additional Information: More detailed studies examining the frequency and context of GZ file exploitation in real-world scenarios would be beneficial. This could include data on how often GZ files are involved in successful cyberattacks compared to other file types.

Conclusion

Verdict: Partially True

The claim that GZ files are safe is partially true. Evidence indicates that while the GZ format itself does not inherently pose a significant risk, it can be exploited by malicious actors who disguise harmful files as GZ files. Reports of malware campaigns utilizing GZ files and the potential for confusion with other file types underscore the need for caution.

However, the context in which GZ files are used, including their source and the practices of the user, plays a critical role in determining their safety. The evidence available is limited and often anecdotal, suggesting that while there are valid concerns, comprehensive data on the frequency and impact of GZ file exploitation is lacking.

Readers are encouraged to critically evaluate information regarding file safety and to exercise caution when handling files from untrusted sources, regardless of their format.

Sources

1. StopRansomware: Medusa Ransomware. CISA. Link
2. Known Indicators of Compromise Associated with ... CISA. Link
3. Understanding CVE-2022-1271: GZIP Vulnerability Analysis - Synopsys. Link
4. Don't Trust That .GZ File, It's a CAB in Disguise. Security Boulevard. Link
5. What is Gzip? - Maximizing Cybersecurity with File Compression - ReasonLabs. Link
6. Don't Trust That .GZ File, It's a CAB in Disguise. IronScales. Link
7. How to Prevent Zip File Exploitation | CrowdStrike. Link
8. A Windows filetype update may have complicated cyber threat detection ... TechRadar. Link
9. Can a tar.gz file contain malicious code? Is a Mac ... SuperUser. Link