Pierluigi Paganini June 16, 2021

A new variant of the Mirai botnet, tracked as Moobot, was spotted scanning the Internet for vulnerable Tenda routers.

Researchers from AT&T Alien Lab have spotted a new variant of the Mirai botnet, tracked asu Moobot, which was scanning the Internet for the CVE-2020-10987 remote code-execution (RCE) issue in Tenda routers. The botnet was linked to a new malware hosting domain that has been serving Mirai variants for several different botnets over the past year.

The experts pointed out that this vulnerability is not commonly targeted by web scanners.

“During the end of March, AT&T Alien Labs observed a spike in exploitation attempts for Tenda Remote Code Execution (RCE) vulnerability CVE-2020-10987. This spike was observed throughout a significant number of clients, in the space of a few hours.” reads the analysis published by AT&T Alien Labs. “This exploit can be identified by the URL that is requested, which includes ‘setUsbUnload’ with the payload assigned to the vulnerable parameter ‘deviceName’. This payload contains the logic to change the execution path to a temporary location, wget a file from a malware hosting page, provide execution permissions, and execute it.”

Experts noticed that the scan for the CVE-2020-10987 flaw only lasted one day, anyway, they noticed that the same malware hosting domain was involved in activities targeting other vulnerabilities:

• Port 80 and 8080: Axis SSI RCE.
• Port 34567: DVR scanner attempting default credentials for Sofia main video application.
• Port 37215: Huawei Home routers RCE Vulnerability (CVE-2017-17215).
• Port 52869: Realtek SDK Miniigd UPnP SOAP Command Execution (CVE-2014-8361).

All the variants had in common the same malware hosting page, dns.cyberium[.]cc, further investigations allowed the researchers to date some of the campaigns back at least to May 2020. Experts also noticed that the domain was hosting several Mirai variants that were used in campaign that lasted for approximately a week.

Each campaign was using a different subdomain page under the Cyberium domain, and once the attacks were terminated the associated subdomains became unresolvable.

“During the time this domain was available and delivering malware, at least three different variants of Mirai were identified: Moobot, Satori/Fbot, and other samples unassociated with these botnets. One of the peculiarities of this domain was how it juggled between Mirai variants, even under the same filenames. The same URL could be hosting Satori one day and Moobot the week after.” continues the report.

Upon compromising an IoT device, the malicious code connects to the Cyberium domain to retrieve a bash script that is used as a downloader similarly to other Mirai variants.

Then the script attempts to download a list of filenames (associated with different CPU architectures), executes each one of them, achieves persistence through a crontab, and deletes itself.

The Moobot botnet was first spotted in April 2020 while targeting multiple types of fiber routers. In October a new variant of the Moobot botnet was spotted targeting vulnerable Docker APIs. The botnet was designed to carry out distributed denial of service (DDoS) attacks like the original Mirai bot.

One of the main distinctions of the Moobot botnet is the presence of a hardcoded string that’s used several times throughout the code.

“Many samples available at Cyberium contained the above-mentioned string and this domain was already being used to distribute this botnet when Lacework first reported on it.  The number of samples Alien Labs has seen with that string has greatly increased in the last months, scattering from the original Moobot sample,” continues the report. “This could potentially mean that last year’s Moobots samples were used to create new branches of Mirai variants.”

According to AT&T, Cyberium domain was still active but at the time of the analysis, it was not hosting any malware samples, likely because the subdomain pages are awaiting new requests for command-and-control server (C2) lists.

“Several questions remain unanswered,” researchers conclud. “Why would the attackers deliver different Mirai variants with different C2s on the same campaign? Are they trying to avoid anti-virus detection through diversification of variants? Or, are they trying to improve the botnet resiliency by diversifying C2.”

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Pierluigi Paganini

(SecurityAffairs – hacking, ransomware)

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