Rizo is a family of IRC bot-based backdoors with network worm capabilities.
For general instructions on disinfecting a local network infection, please see Eliminating A Local Network Outbreak.
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Rizo malware can spread itself to remote computers with the help of an exploit. Unlike many other exploits that download a copy of malware from an already infected computer, Rizo's exploit downloads and runs a file from a website. Every time this website is accessed, a repacked variant is offered for download.
Rizo is a backdoor-worm that spreads within local networks and via the Internet. When it arrives on an infected computer it copies itself to the Windows System folder with the name ofwinlogin32.exe and creates several startup strings in the Registry:
Being active, the backdoor connects to the following IRC servers:
Then the malware joins an IRC channel named #!v21! using the password 'tn10a4' without quotes. The port for connection is 8008.
The Rizo backdoor-worm can do any of the following:
The URL above can be also used to upgrade the copy of the backdoor. At the moment the page contains only the text string 'EMPTY'.
The exploit in the backdoor's body is partially encrypted. When sent over to a target computer, the exploit decrypts itself (simple XOR 0x99 operation), resolves several APIs, downloads a file to the Windows System folder from the dl1.debelizombi.com website and runs it. The name of the downloaded file is a.exe.