[NT] AntiVirus Filename Bypassing

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  AntiVirus Filename Bypassing
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SUMMARY

Several AntiVirus programs do not scan filesnames that contain 
non-printable ASCII characters, in addition instead of blocking them they 
are simply ignored.

DETAILS

Vulnerable Systems:
 * BitDefender Antivirus
 * Trustix Antivirus
 * Avast! Antivirus
 * Cat Quick Heal Antivirus
 * Abacre Antivirus
 * VisNetic Antivirus (bypass only with manual scan)
 * AntiVir Personnal Edition Antivirus
 * Clamav for Windows Antivirus
 * Lavasoft Adware SE Personal Edition
 * Antiy Ghostbusters Professional Edition

Immune Systems:
 * Kaspersky Antivirus
 * AVG Free

Several AntiVirus programs do not scan files that contain extended ASCII 
characters and characters that are lower than 0x20. An attacker can rename 
a malicious filename to such a filename which in turn will cause the 
AntiVirus programs to ignore the filename.

Proof of Concept:
If your Antivirus options are:
 - "Scan on accessed files"
 - "A real time protection"
If you want to test this PoC, don't forget to temporarily disabling before 
handling!

Select only a "detected" program that does not have to disturb the correct 
operation of your machine!

Find a program detected by your software protection.
BitDefender for example don't like ClearLogs.

ClearLogs clears the local or remote event log computer.
Ref: http://ntsecurity.nu/downloads/clearlogs.exe
BitDefender >> Detected: Application.Clearlog.A

Rename clearlogs.exe to clearlogs[Here press Alt + 1].exe
Alt + "some numbers" generate specials ASCII characters.
Ref: http://www.lookuptables.com

After that re-activate the real time protection.
Then if you scan it ...
[100%] "Scan successful: no viruses found"

Open your CMD and execute.
X:\SecuBox.Labs\clearlogs ~ .exe
    ClearLogs 1.0 - (c) 2002, Arne Vidstrom
    Usage: clearlogs [\\computername] <-app / -sec / -sys>

            -app = application log
            -sec = security log
            -sys = system log

If we take a look to [Show report] - Statistics
Scan path: X:\SecuBox.Labs\clearlogs?.exe
 Folders: 0
 Files: 4
 Archives: 0
 Packed files: 0
 Identified viruses: 0
 Infected files: 0
 Warnings: 0
 Suspect files: 0
 Disinfected files: 0
 Deleted files: 0
 Copied files: 0
 Moved files: 0
 Renamed files: 0
 I/O errors: 0
 Scan time: 00:00:01
 Scan speed (files/sec): 4


ADDITIONAL INFORMATION

The information has been provided by  <mailto:unsecure@xxxxxxxxxxx> 
SecuBox Labs.



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