Danish critical infrastructure faced the biggest online attack in the country’s history in May, according to SektorCERT, Denmark’s specialist organization for the cybersecurity of critical kit.
Detailing the attack waves in a report, it revealed that 22 companies were breached in just a few days. Some were forced to enter island mode operation, where they had to disconnect from the internet and cut any other other non-essential network connections.
In almost all cases unpatched vulnerabilities in Zyxel firewalls meant compromise was possible, and in some the attackers appeared well-resourced, exploiting vulnerabilities that weren’t publicly announced (zero days).
