Berlin's Official Portal Disrupted by DDoS Attack: Technical Analysis and Response

Berlin’s official government portal, berlin.de, remains partially inaccessible following a distributed denial-of-service (DDoS) attack that began on April 25, 2025. The Senate Chancellery confirmed the cyberattack but has not attributed it to any specific threat actor. This incident mirrors a 2023 attack on Berlin and Potsdam’s infrastructure, which was linked to pro-Russian hacker groups¹.

Attack Overview and Impact

The DDoS attack targeted both berlin.de and its service platform, service.berlin.de, overwhelming servers with traffic from botnets. Unlike the 2023 incident, this attack demonstrated higher sophistication in its execution². Critical services affected include citizen appointment systems and police portals, though emergency reporting via “Internetwache” remains functional. The Senate confirmed no evidence of data exfiltration, indicating the attack’s primary goal was disruption³.

Technical analysis reveals the attack exploited vulnerabilities in Berlin’s Imperia CMS, a content management system widely used by German municipalities. This caused cascading failures in intranet operations, complicating mitigation efforts⁴. The Berlin Senate has deployed cloud-based failovers and is collaborating with the Federal Office for Information Security (BSI) for forensic analysis⁵.

Technical Response and Workarounds

Authorities have advised citizens to use the federal portal or call hotline 115 for urgent services. The Bundesportal’s infrastructure, which operates independently of Berlin’s systems, has remained unaffected⁶. Meanwhile, the police union (GdP) criticized Berlin’s lack of redundant systems, with spokesperson Stephan Weh stating, “A single hacker can cause immense damage. We lack fallback systems despite daily attacks”⁷.

Network telemetry from status.berlin.de shows fluctuating attack intensity, with renewed surges on April 28. This pattern suggests automated tools or intermittent botnet activation⁸. The Senate has not disclosed specific mitigation techniques but confirmed the use of rate-limiting and traffic filtering through partnerships with German ISPs.

Historical Context and Political Reactions

The 2025 attack shares technical similarities with the 2023 incident, including identical DDoS patterns and target selection. However, the Senate has not confirmed a connection to pro-Russian groups this time⁹. Opposition parties have called for an audit of Berlin’s cyber defenses, citing recurring vulnerabilities in critical infrastructure¹⁰.

Germany’s Federal Interior Ministry noted that at least six other cities faced similar DDoS attacks in Q1 2025, though none reached Berlin’s severity. This aligns with broader trends of increasing attacks on European municipal systems¹¹.

Security Recommendations

For organizations facing similar threats, consider these mitigation steps:

Implement cloud-based DDoS protection services with automatic scaling
Deploy redundant CMS instances across geographically separate data centers
Conduct regular stress tests on public-facing portals
Maintain offline fallback procedures for critical citizen services

The Berlin incident underscores the need for layered defenses against volumetric attacks, particularly for government portals handling sensitive citizen data. While attribution remains challenging, the attack’s persistence suggests either ideological motivation or testing of defensive responses.