Bsd updating clamav
Will all of those clients be using a Linux operating system? Because of this, the email your server sends out has to be free from viruses or else those Windows clients will become crippled. And on the Linux platform, one of the easiest to integrate into Postfix is Clam AV.
If we take a look at our test signature, it’s quite clear that the signature name is “Eicar-Test-Signature”, the target file is 0 (which means any file type), the offset is 0, and the hexadecimal signature is: 58354f2150254041505b345c505a58353428505e2937434329377d2445494341522d5354414e444152442d414e544956495255532d544553542d46494c452124482b482a.
The hexadecimal signature can also have wildcards that correspond to regular expressions when searching for some signature in the files. a : match the low four bits – * : match any number of bytes – : match n bytes – : match n or less bytes – : match n or more bytes – : match between n and m bytes – (aa|bb) : match aa or bb – !
By standardization, every antivirus software must be able to detect the eicar test virus.
The contents of the eicar test virus are presented below: We can see it’s just some gibberish that doesn’t actually do anything. If we scan the with Clam AV, it is detected as a virus, which can be seen below: # clamscan -i -r eicar.com: Eicar-Test-Signature FOUND ----------- SCAN SUMMARY ----------- Known viruses: 1301403 Engine version: 0.97.5 Scanned directories: 0 Scanned files: 1 Infected files: 1 Data scanned: 0.00 MB Data read: 0.00 MB (ratio 0.00:1) Time: 4.530 sec (0 m 4 s) # grep "Eicar-Test-Signature" Eicar-Test-Signature:0:354f2150254041505b345c505a58353428505e2937434329377d2445494341522d5354414e444152442d414e544956495255532d544553542d46494c452124482b482a Eicar-Test-Signature-1:0:*:574456504956416c51454651577a5263554670594e54516f554634704e304e444b5464394a45564a513046534c564e555155354551564a454c55464f56456c5753564a565579315552564e550a4c555a4a544555684a45677253436f3d0a # sigtool -f "Eicar-Test-Signature" [main.ndb] Eicar-Test-Signature:0:354f2150254041505b345c505a58353428505e2937434329377d2445494341522d5354414e444152442d414e544956495255532d544553542d46494c452124482b482a [main.ndb] Eicar-Test-Signature-1:0:*:574456504956416c51454651577a5263554670594e54516f554634704e304e444b5464394a45564a513046534c564e555155354551564a454c55464f56456c5753564a565579315552564e550a4c555a4a544555684a45677253436f3d0a The ASCII representation is exactly the same as the contents of the test virus file.
We could change the string to look for similar variations of the string and save the signatures in a new database
When running clamscan afterwards, we need to specify the new database to search in with the -d command line parameter.
But I would not advise you to use that switch, because of false positives.
If the Clam AV mistakenly identifies non-malicious file as being infected and thus malicious, it will delete it without making a backup.
What follows is the target parameter, which specifies the type of the file to match.
Afterward there’s an offset representing a specific position in the file and a hexadecimal signature.
This way we can check if the file is indeed malicious and delete it ourselves.Tags: Adult Dating, affair dating, sex dating