Home / News

Denmark Encounters Largest Cyber Attack on Its Critical Infrastructure to Date

Photo: SektorCERT

Denmark experienced its largest-ever cyberattack in May, targeting the nation’s critical infrastructure. SektorCERT, the Danish cybersecurity authority, reported breaches in 22 companies within days. Many resorted to ‘island mode,’ isolating themselves from the internet to contain the threat.

SektorCERT has released a full report on the attack — here are some key takeaways:

Vulnerability exploitation: The attackers exploited unpatched flaws in Zyxel firewalls, a common device among SektorCERT-protected organizations. Some breaches involved sophisticated zero-day vulnerabilities, suggesting well-resourced assailants. SektorCERT suspects involvement from multiple hacker groups, including Russia’s GRU-affiliated Sandworm.

Many organizations were caught off-guard, assuming their new firewalls had the latest software or that vendors were responsible for updates. Some avoided updates due to additional costs, while others were unaware of Zyxel devices in their network. This oversight gave attackers ample time, even after SektorCERT’s alerts.

Waves of Attack

Initial breach and reconnaissance: Starting May 11, 16 energy organizations were targeted, exploiting a specific vulnerability (CVE-2023-28771). Eleven were immediately compromised, possibly due to reconnaissance efforts, as attackers harvested firewall configurations and credentials.

Coordinated assault: The first attack wave displayed remarkable coordination, requiring significant planning and resources. A 10-day quiet period followed, after which a second wave commenced. This included using an already-compromised organization to launch DDoS attacks as part of the Mirai botnet, targeting entities in the US and Hong Kong.

Continuous Compromises and Responses

Escalating threats: Following the initial attacks, SektorCERT tirelessly countered further breaches through Zyxel firewalls. In one case, a compromised firewall led to the loss of remote location visibility, forcing manual interventions.

A final wave of attacks, linked to the Russian cyber unit Sandworm, disrupted but did not significantly impact Denmark’s critical infrastructure. SektorCERT applauded the swift and professional response of its team and the affected organizations.

SektorCERT has emphasized the need to address systemic vulnerabilities to protect Denmark’s critical infrastructure from persistent foreign cyber threats.

NORDVPN DISCOUNT - CircleID x NordVPN
Get NordVPN  [74% +3 extra months, from $2.99/month]
By CircleID Reporter

CircleID’s internal staff reporting on news tips and developing stories. Do you have information the professional Internet community should be aware of? Contact us.

Visit Page

Filed Under

Comments

Comment Title:

  Notify me of follow-up comments

We encourage you to post comments and engage in discussions that advance this post through relevant opinion, anecdotes, links and data. If you see a comment that you believe is irrelevant or inappropriate, you can report it using the link at the end of each comment. Views expressed in the comments do not represent those of CircleID. For more information on our comment policy, see Codes of Conduct.

CircleID Newsletter The Weekly Wrap

More and more professionals are choosing to publish critical posts on CircleID from all corners of the Internet industry. If you find it hard to keep up daily, consider subscribing to our weekly digest. We will provide you a convenient summary report once a week sent directly to your inbox. It's a quick and easy read.

Related

Topics

New TLDs

Sponsored byRadix

Brand Protection

Sponsored byCSC

DNS

Sponsored byDNIB.com

Cybersecurity

Sponsored byVerisign

Threat Intelligence

Sponsored byWhoisXML API

IPv4 Markets

Sponsored byIPv4.Global

Domain Names

Sponsored byVerisign