Avira Researchers Discover a New Variant of Mirai

The botnet, named Katana, is still in development but already has modules such as layer 7 DdoS, unique encryption keys, fast self-replication, and secure C&C, making it a more serious threat

October 27, 2020

3 Min Read


October 26, 2020 (TETTNANG, GERMANY) – The Avira Protection Lab recently identified a new variant of the Mirai botnet which is Katana after the Japanese sword. Although the Katana botnet is still in development, it already has modules such as layer 7 DDoS, different encryption keys for each source, fast self-replication and secure connection to the command-and-control server (C&C). There is evidence that Katana may be linked to an HTTP banking botnet in the future.

Last June, the Avira Protection Lab reported on how the Mirai IoT botnet has evolved since its source code was made public in 2017. A recent analysis of Avira on IoT attacks and malware trends shows that Mirai is constantly evolving and can be bought via YouTube channels, in this case the channel  VegaSec. Easy access and  other changes also allow unskilled attackers to create malicious botnets, which could lead to a  steady increase in botnet-guided IoT attacks.

Katana Analysis

Over the past two weeks, Avira’s Honeypot captured a wave of unknown malware binaries. As a result of that  the, Avira team decided to research further and found the following: By executing remote codes and command injection, the Katana botnet attempts to exploit old security vulnerabilities in (older) LinkSys and GPON routers. Although Katana uses old exploits – Avira assumes that Katana is in the testing and development phase – it has nevertheless caught the attention of the Avira IoT research team, because:

  • It includes classic Mirai functions such as running a single instance, random process name, manipulating the watchdog to prevent the device from restarting,

  • Similar to Mirai, it offers various DDoS commands such as 'attack_app_http' or 'attack_get_opt_int'.


Currently, Katana is actively infecting hundreds of devices each day, with the top 3 based on Avira stats being:

  • DSL-7740C DLink

  • DOCSIS 3.1 Wireless Gateway

  • Dell PowerConnect 6224 Switch

Katana is downloaded from different IP addresses within a certain period of time.  Data from Avira proves how the download process works. The Katana IoT botnet runs as a single instance by binding different ports.

"Katana contains several features of Mirai. These include running a single instance, a random process name, editing the watchdog to prevent the device from restarting, and DDoS commands," said Alexander Vukevic, Director of Avira Protection Labs.  "The problem with new Mirai variants like Katana is that they are offered on the DarkNet or via regular sites like YouTube, allowing inexperienced cybercriminals to create their own botnets."  


Note to Editors: Click here for image of Alexander Vukcevic, logos, and other assets.

About Avira

Avira provides a consumer-focused portfolio of security and privacy solutions for Windows and Mac computers, Android and iOS smartphones, home networks, and smart devices (IoT). All Avira features are available as licensed SDKs and APIs. Working together, Avira and its partners protect more than 500 million devices globally. Avira solutions consistently achieve best-in-class results from independent security tests. 

Avira is a privately held company headquartered near Lake Constance, Germany, with additional offices in the EU, the United States, and Asia. For more information about Avira visit www.avira.com.

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