KillNet hits healthcare sector with DDoS attacks

At the end of January, the Health Sector Cybersecurity Coordination Center warned that the KillNet group is actively targeting the US healthcare sector with distributed denial-of-service (DDoS) attacks.

The Cybersecurity and Infrastructure Security Agency (CISA) says it helped dozens of hospitals respond to these DDoS incidents.


A distributed denial-of-service attack uses numerous systems to send network communication requests to one specific target. Often the attackers use enslaved computers, “bots”, to send the requests. The result is that the receiving server is overloaded by nonsense requests that either crash the server or keep it so busy that normal users are unable to connect to it.

This type of attack has been popularized by numerous hacker groups, and has been used in state-sponsored attacks conducted by governments. Why? Because they are easy to pull off and hard to defend against.


KillNet is a pro-Russian group that has been notably active since January 2022. Until the Russian invasion of Ukraine, KillNet was known as a DDoS-for-hire group. Now they are better known for the DDoS campaigns launched against countries supporting Ukraine. In previous campaigns the gang has targeted sites belonging to US airlines, the British royal family, Lithuanian government websites, and many others, but now their main focus has shifted to the healthcare sector. Not for the first time by the way—the group has targeted the US healthcare industry in the past too.

These attacks are not limited to the US. Recently, the University Medical Center Groningen (UMCG) in the Netherlands saw its website flooded with traffic. That attack was attributed to KillNet by the country’s healthcare computer emergency response team, Z-CERT.

The KillNet group runs a Telegram channel which allows pro-Russian sympathizers to volunteer their participation in cyberattacks against Western interests. This sometimes makes it hard to attribute the attacks to this particular group since the attacks will originate from different sources.

The attacks

KillNet’s DDoS attacks don’t usually cause major damage, but they can cause service outages lasting several hours or even days. For healthcare providers, long outages can result in appointment delays, electronic health records (EHRs) being unavailable, and ambulance diversions.

According to CISA, only half of the KillNet attacks have been able to knock websites offline. CISA says it worked with several tech companies to provide free resources to under-funded organizations that can help them reduce the impact of DDoS attacks. It also plans to continue working with the US Department of Health and Human Services (HHS) to communicate with hospitals about government assistance and third-party services.


Although it can be difficult to mitigate DDoS risks, the Health Sector Cybersecurity Coordination Center (HC3) is encouraging healthcare organizations to enable firewalls to mitigate application-level DDoS attacks and use content delivery networks (CDN).

Scrambling for a solution at the moment you find out that you are the target of a DDoS attack is not the best strategy, especially if your organization depends on Internet-facing servers. So, if you don’t have an “always-on” type of protection, make sure you at least have a plan or protocols in place that you can follow if an attack occurs.

Depending on the possible consequences that would do the most harm to your organization, the chosen solution should offer you one or more of these options:

  • Allow users to use the site as normally as possible.
  • Protect your network from breaches during an attack.
  • Offer an alternative system to work from.

The least you should do is make sure you’re aware of the fact that an attack is ongoing. The sooner you know what’s going on, the faster you can react in an appropriate manner. Ideally, you want to detect, identify, and mitigate DDoS attacks before they reach their target. You can do that through two types of defenses:

  • On-premise protection (e.g. identifying, filtering, detection, and network protection).
  • Cloud-based counteraction (e.g. deflection, absorption, rerouting, and scrubbing).

The best of both worlds is a hybrid solution that detects an attack on-premise early on and escalates to the cloud-based solution when it reaches a volume that the on-premise solution cannot handle. Some DDoS protection solutions use DNS redirection to persistently reroute all traffic through the protectors’ network, which is cloud-based and can be scaled up to match the attack. From there, the normal traffic can be rerouted to the target of the attack or their alternative architecture.

CISA encourages all network defenders and leaders to review these three documents:

Ransomware warning

Several security agencies and providers have warned that DDoS attacks are being used as cover for actual intrusions involving ransomware and data theft. In these attacks, the DDoS acts as a smokescreen, drawing attention from the far greater danger posed by the ransomware.

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