Miscreants have developed a ransomware package that blocks internet access in a bid to force infected users into paying up by sending a text message to a premium rate SMS number, lining the pocket of cybercrooks in the process.
The malware comes bundled in a package called uFast Download Manager and targets potential marks in Russia. Users of infected machines are told (via a Russian language message) that they need to send a text message in order to obtain an activation code for the product, which (ironically) poses as a software package designed to increase download speeds. Victims are told that internet access has been blocked in the meantime because of supposed violations of a licensing agreement.
The ploy is a variant on previous ransomware packages that encrypt and block access to document files. One strain of ransomware detected in January 2008 locks up Windows machines, seeking payment via SMS. That threat wasn't specific to Russia and didn't affect a net connection as such but is otherwise very similar to the latest attack.
CA, which detects the threat as RansomSMS-AH, explains how the malware works in greater depth in a blog posting featuring screenshots culled from infected machines here. The anti-virus vendor has developed an activation code generator that allows victims to get online again - providing they can download the utility through an uninfected machine first, of course. ®