Sophos

Troj/Chast-A

Aliases
  • Trojan-Spy.Win32.KeyLogger.ao
  • Keylog-Chast
  • Win32/Spy.KeyLogger.AO
  • TROJ_KEYLOGER.AO
Category
Type
What to do
Prevalence low high

Summary

 
Affected operating systems Windows
Characteristics
  • Drops more malware
  • Installs itself in the registry
Included in our products from February 2006 (4.02)
Protection available since 22 November 2005 22:16:00 (GMT)
Last updated 2 December 2005 14:04:23 (GMT)
Detected by All Sophos products

Action

More Information

Troj/Chast-A is a backdoor and keylogging Trojan for the Windows platform.

When first run Troj/Chast-A copies itself to <Windows>\<random>.exe and creates the following files:

<Windows>\isnopt.dat
<Windows>\isnsys.dll
<Windows>\isnsys32zx.dll
<System>\isndata\data\<Username>\logapps.dat
<System>\isndata\data\<Username>\logwin.dat

The file isnsys32zx.dll is detected as Troj/Wilcol-A, and may be used to stealth Troj/Chast-A. The dat files are clean data files, and may safely be deleted. The file isnsys.dll is the keylogging component of the Trojan, and is also detected as Troj/Chast-A.

Troj/Chast-A can also log Instant Messaging conversations, as well as retrieve information about infected systems.

The following registry entry is created to run win16svc.exe on startup:

HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
System32Check
<Windows>\<random>.exe

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