"When a user clicks on the link in the attack e-mail," the technology service desk helpfully explains to the nation's less-than-savvy Congresspeople, "the malware encrypts all files on that computer, including shared files, making them unusable until a 'ransom' is paid. The recent attacks have focused on using .js files attached as zip files to e-mail that appear to come from known senders."
While it would be amusing to find out if any representatives or their staff were hapless enough to click on a suspicious email attachment, a spokesperson for the House Chief Administrative Officer wouldn't confirm to TechCrunch whether or not the attacks were successful. In addition to YahooMail, it appears a number of Google Apps were also blocked.
Congress isn't alone as a target for ransomware attacks, however. Earlier this year, hackers held the computer system hostage at a hospital in Los Angeles. The medical center was eventually forced to hand over 40 bitcoins (or about $17,000) to get its network back. Likewise, the aging computer systems at many schools make them a prime target for ransomware attacks.