Hacktivists have claimed responsibility for a Distributed Denial-of-Service (DDoS) attack that has taken down the public-facing infrastructure of popular Linux operating system Ubuntu and its parent company Canonical.

The attack began on Thursday, resulting in outages affecting several Ubuntu and Canonical websites. According to a post on an unofficial Ubuntu community forum, the DDoS attack is targeting Ubuntu’s security API, making it impossible for users to update or install the software. TechCrunch verified that updates failed to install on a test device running Ubuntu.

As of writing, the outage has been ongoing for around 20 hours. Canonical stated in an official message: “Canonical’s web infrastructure is under a sustained, cross-border attack and we are working to address it.” Hacktivists calling themselves The Islamic Cyber Resistance in Iraq 313 Team took credit on their Telegram channel.

The use of DDoS-for-hire services, which allow anyone with money to launch attacks without technical skills, highlights the ongoing challenge for authorities. For years, agencies such as the FBI and Europol have struggled against these services, taking down domains and sometimes arresting those behind them.