We're gradually updating threat actor names in our reports to align with the new weather-themed taxonomy. Learn about Microsoft threat actor names
Win32/Cissi
Detected by Microsoft Defender Antivirus
Aliases: No associated aliases
Summary
Windows Defender Antivirus detects and removes this threat.
Win32/Cissi is a mass-mailing and network worm with a backdoor component. The worm can spread to remote NetBIOS shares by trying weak account name and password combinations. Some variants of the worm can gather email addresses from the infected computer and send a copy of the worm to those addresses as an e-mail attachment. Win32/Cissi has an additional component that connects to an IRC server to serve as a backdoor.
Use the following free Microsoft software to detect and remove this threat:
- Microsoft Defender Antivirus for Windows 10 and Windows 8.1, or Microsoft Security Essentials for Windows 7 and Windows Vista
- Microsoft Safety Scanner
You should also run a full scan. A full scan might find hidden malware.
Get more help
You can also visit our advanced troubleshooting page or search the Microsoft virus and malware community for more help.
If you’re using Windows XP, see our Windows XP end of support page.
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