CAVFree x64 v 4.0.135239.742 corrupts EFS encrypted files on Win7 Pro 64-bit

Comodo Antivirus Free x64 version 4.0.135239.742 running on Windows 7 Pro 64-bit causes data corruption of EFS encrypted files (Windows Encrypting File System).

Specifically, files that are EFS encrypted are fine until the system is shut down and restarted. After that, some or all (at random) of the EFS encrypted files have corrupted data. For example, plain text files have scrambled content appearing like binary data (graphic symbols, foreign symbols and gibberish). Other files, such as Office documents will not load due to the file format being unrecognized by their host apps.

After subsequent shutdown/restarts, some EFS encrypted files may return to normal, while other EFS encrypted files that were previously normal become scrambled. I even had one text file that had some normal data and the rest scrambled, within the same file.

Note that the files are accessible–there is no access denial–and the files’ properties show that the correct digital certificate is being used to encrypt the files.

I found this after reading a posting at another security forum by someone who was having exactly the same problem, but reported that it was being caused by Symantec anti-virus software. I have used only Comodo anti-virus and my system is completely clean of anti-virus software from any other vendors. So, I removed the Comodo anti-virus software, and sure enough, the problem has gone away. I have been through a dozen shutdown/restarts now and have had no further corruption of EFS encrypted files since I removed the Comodo anti-virus software.

In conclusion, I am disappointed because I really liked the Comodo AV Free software; but alas, EFS file encryption is a critical function that I can’t do without and I must be able to trust the data integrity of my encrypted files.

you can always exclude those files from being scanned by the AV. It’s under the av tab, scanner settings, exclusion. Also I hope you are not just using the antivirus, the real power of comodo comes from the whole suite, you are missing the firewall, HIPS ( defense plus) and sandbox.


Thanks, but this thread is for bug reports, not questions about how to use the software. I know about exclusions, but that is not a solution to this problem. It’s more like sweeping a bug under the rug, which doesn’t get rid of it. I don’t want to be bothered with adding/removing exceptions every time I encrypt/decrypt files. Defense+, Firewall, etc., are irrelevant to this post.

An easy, albeit inadequate, fix would be to add an option (e.g., checkbox) for excluding all encrypted files from virus scanning. However, since many recent malware threats use encryption, including EFS encyption, to mask their presence, this approach would not be secure. I don’t know what the solution is–I’ll leave that to better minds–but this problem will have to be addressed sooner or later.

same problem, i dint know it was CIS who was corruptin my encrypted files until now that i search in google and get to another forum were someone says that comodo antivirus is the problem.
i hope its fixed soon
this is what i know so far
both 32/64bits cause the problem
it happens at random reboot
most ppl having this problem have windows 7 64
apparently others antivirus may do it

Languy, sorry, I’m with Dawkcodave.
It’s not a firewall or HIPS problem.
Acknowledge and correct is the attitude imho.

I’ve observed this Comodo/EFS bug for over 1 year.

I’ve seen it happen with .TXT files and .DOC (MS Word) files, but not any others (so far).

The problem was observed when running Comodo free version 3 almost 1 year ago,
and is still present in Comodo free version 4.1.150349.920 now.

If I disable Comodo’s real time virus scan then the problem goes away.

I’m running XP Pro so it’s not limited to Vista or Win 7 as the closed post “” says. By the way, why is that post closed and listed as “Resolved/Outdated Bugs” when it’s neither Resolved nor Outdated?!

Anyway, besides this problem, I think Comodo’s a very good product. Well done! :slight_smile:


wron, it can happen to any file, a year ago i was getting images corrupted, and this week there was a couple of docs an rar files
so this bugs happen in any OS and any file

I 'm testing the latest Comodo CIS 5.3.176753.1236 since two week and I have encountered this serious problem: randomly some EFS encrypted files become corrupted.
The Hard-disk hasn’t problems.

My OS is Windows 7 x86 all service pack installed.