Published May 21, 2011 | Updated Sep 15, 2017


Severe |Detected with Windows Defender Antivirus

Aliases: Win-Trojan/Zaccess.25600.B (AhnLab) Backdoor.Win32.ZAccess.dg (Kaspersky) W32/ZAccess.G (Norman) Backdoor.ZAccess!W3R2wlUUEiQ (VirusBuster) Backdoor.Win32.ZAccess (Ikarus) Trojan.Zeroaccess (Symantec) TROJ_SPNR.0BHE11 (Trend Micro)


Backdoor:Win32/Smadow is a trojan that can perform different actions, such as executing other malware, which may be detected as TrojanDropper:Win32/Sirefef.B or Trojan:Win32/Sirefef.

To detect and remove this threat and other malicious software that may be installed on your computer, run a full-system scan with an appropriate, up-to-date, security solution. The following Microsoft products detect and remove this threat:

For more information on antivirus software, see

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