MikroTik Confirms Mēris Botnet Targets Routers Compromised Years Ago

The recently detailed Mēris botnet is targeting devices that were originally compromised three years ago, Latvian network equipment maker MikroTik says.

Capable of launching record-breaking distributed denial-of-service (DDoS) attacks, the botnet has only been around for several months, but security researchers believe it already has more than 200,000 bots. Overall, however, more than 328,000 routers are potentially at risk.

The vast majority of the vulnerable devices, security researchers have discovered, are MikroTik routers running various versions of RouterOS. Many of the devices apparently run a stable iteration prior to the last.

According to MikroTik, the bots are in fact routers that were previously compromised in 2018, and which haven’t been properly secured, even if the patches released at the time were installed in a timely manner.

“Unfortunately, closing the vulnerability does not immediately protect these routers. If somebody got your password in 2018, just an upgrade will not help. You must also change password, re-check your firewall if it does not allow remote access to unknown parties, and look for scripts that you did not create,” a MikroTik employee notes in a forum post.

The company also underlines that the attacks don’t target a new, undisclosed vulnerability, and that users who applied the patches and also reset their passwords are protected.

MikroTik also says that it attempted to inform potentially affected users of the situation, but notes that the operation hasn’t been successful because “many of them have never been in contact with MikroTik and are not actively monitoring their devices.”

Although no new security flaw is being targeted, MikroTik does encourage users to check their devices for malicious scripts or unknown SOCKS configurations and to contact the company if one such configuration has appeared recently on a device running a new RouterOS release.

“More specifically, we suggest to disable SOCKS and look in the System -> Scheduler menu. Disable all rules you can’t identify. By default, there should be no Scheduler rules, and SOCKS should be off,” the company says.

Mēris is capable of launching record-breaking application-layer DDoS attacks and is believed to have been responsible for the largest such assaults ever, which peaked at 17.2 million requests per second (RPS) and 21.8 million RPS, respectively.

The same botnet appears to be responsible for a new DDoS attack on the website of investigative journalist Brian Krebs. Peaking at roughly 2 million RPS, the attack was much smaller than those observed over the past few weeks, but even so, it was four times more powerful than a 2016 attack on the same site.

Related: Mēris Botnet Flexes Muscles With 22 Million RPS DDoS Attack

Related: Akamai Sees Largest DDoS Extortion Attack Known to Date