If so, then you're likely dealing with "ransomware" known as Reveton, which freezes PCs and opens a window telling people that if they want to regain control, they'll need to pay a "fine" via a prepaid money card service. Helpfully, a "pay MoneyPak" code-entry box is even helpfully included on the lock screen. But unlocking a Reveton-infected PC can be difficult, owing to the malware often being deployed in conjunction with other malware that's designed to block users from accessing security websites.
The FBI last week issued a warning that the number of Reveton infections has recently been surging. "We're getting inundated with complaints," said Donna Gregory, a manager at the Internet Crime Complaint Center (IC3), which is a joint effort between the FBI and the National White Collar Crime Center, in a statement. "Some people have actually paid the so-called fine," she said, noting that amounts of $200 aren't uncommon.
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"Instructions were given on how to load the card and make the payment," one victim of the scam wrote in an emailed complaint to the IC3. "The page said if the demands were not met, criminal charges would be filed and my computer would remain locked on that screen."
Some versions of the scam pretend to be from the FBI, while others list the Department of Justice's Computer Crime and Intellectual Property Section as being behind the freeze. Regardless, the warning notices are heavy on the legalese, accusing PC owners of everything from "violating Article 202 of the Criminal Code" to distributing child pornography. According to the FBI, some versions of Reveton even "turn on computer webcams and display the victim's picture on the frozen screen."
Most Reveton infections also seem to be the result of "drive-by viruses," said the FBI, referring to PCs being infected via known vulnerabilities when they visit a compromised website, rather than through phishing attacks or tricking users into opening malicious email attachments.
The Reveton ransomware is typically delivered via Citadel Trojan malware, according to the FBI's warning. Based on the Zeus malware, Citadel is an all-purpose crimeware kit designed for financial fraud, which debuted on Russian underground hacking websites in December 2011 and sells for $2,500, although plug-ins for adding additional capabilities, as well as a monthly malware-as-a-service update, cost extra.
Citadel's creators have seen rapid uptake of their malware, reportedly owing to high-quality customer service practices, such as frequent updates that add customer-requested capabilities. These include AES encryption to help hide communications between infected "zombie" PCs and its command-and-control server, capabilities for defeating botnet-tracking services, and blocks that stop infected PCs from visiting security vendors' websites or antivirus-signature updating sites.
But according to a July 2012 blog post from a fraud research group at security firm RSA, thanks to law enforcement pressure, Citadel's developer has announced that he's withdrawing the malware from the open--albeit underground--market. "It appears that soon enough only existing customers will continue to enjoy Citadel Trojan upgrades and those wishing to purchase a new kit from the outside will have to get a current customer to vouch for them or be denied the product altogether," according to RSA.
Not everyone, however, is buying the bureau's assertion that Citadel is being used to distribute Reveton. According to security journalist Brian Krebs, a team of Reveton-tracking researchers instead suspects that scammers are using exploit toolkits such as BlackHole to infect PCs with both types of malware.