A recent attack from "ransomware" to the House of Representatives prompted Congress to work with Yahoo on security issues, NBC News reported.
The House Information Security Office advised representatives late last month that it had blocked access to its networks from Yahoo Mail accounts because of the attacks, the business and tech site Fast Company first reported last week.
The attacks used web-based services like Yahoo Mail and Gmail, the IT office said in a memo to members, but "the primary focus appears to be through Yahoo Mail at this time." There was no immediate indication that the attacks extended to the Senate.
According to the memo, the attack uses a social engineering and phishing strategy by generating an email that appears to be from a trusted source. The email includes an attached .ZIP file that, when clicked, injects code that encrypts all files on the recipient's computer — including files shared with other users.