The website for the U.S. Congress was down for a short time Thursday evening and a hacking group known as "Killnet" claimed to have conducted an attack.
Congress.gov was down with users being given an "Error 522" or "Connection timed out" message when trying to access the site. The website went down around 10 p.m. Thursday evening.
Killnet, a pro-Russian hacker group known for DDoS or denial-of-service attacks, claimed it had conducted an attack on the site.
The Library of Congress confirmed the attack in a statement to Fox News Digital.
"Overnight, Congress.gov was targeted by a distributed denial of service (DDoS) network attack that briefly affected public access," the statement said. "The Library of Congress used existing measures to address the attack quickly, resulting in minimal down time. The Library’s network was not compromised and no data was lost as a result of the attack."
A denial-of-service attack is a cyberattack that happens when users are unable to access information systems, devices or other network resources due to the actions of a malicious threat actor, according to the U.S. Cybersecurity & Infrastructure Security Agency.
The agency says the most common method of attack occurs when an attacker floods a network server with traffic causing it to become overwhelmed.
As of around 10:45 p.m. Thursday, Congress.gov was back up and running for some users.
The individual websites for the House and Senate appeared to be unaffected.