New Botnet Uses DHT as Its Foundation

Security researchers at 360 Netlab have been watching a new botnet they call Mozi (from one of the internal files) for the last four months. It's a new P2P botnet with implementation that is based on the Distributed Hash Table (DHT) protocol.

The researchers also say in their post announcing the discovery that "Mozi Botnet relies on the DHT protocol to build a P2P network, and uses ECDSA384 and the xor algorithm to ensure the integrity and security of its components and P2P network. The sample spreads via Telnet with weak passwords and some known exploits." They found that Netgear, D-Link and Huawei routers were easy targets for Mozi.

The DHT protocol used is based on the standard commonly used by torrent clients, but the hash table itself is a custom one. The DHT that is used in creating the botnet's network means that it is done without needing to use servers. It is also much easier to hide the botnet's payload in the large amount of normal DHT traffic, which makes detection of its origins harder than it otherwise might be.

Netlab also says the bot "does reuse part of the Gafgyt code, but it is not really Gafgyt."

The main commands available to the bot include a DDoS attack, collecting information, executing the payload of the specified URL, updating from a specified URL and executing system or custom commands.

The malware first seeks to establish a beachhead by opportunistically exploiting weak or known telnet passwords, such as might be found on a CCTV device or some other IoT mechanism. It starts an http session and then receives the sample download address in the Config file used by Mozi, which is issued by the Botnet Master. Next, it writes the downloader file in echo mode and runs it.

The infected device will run the bot code and then joins the Mozi network, announcing itself as a new node. It will not be a trusted node of the network until it can pass the signature verification routine. Then it will be accepted and used by the Mozi node for nefarious purposes.

As a last step, it looks for other devices to infect. It depends on certain vulnerabilities to extend itself. The blog posts a list of the affected devices, which includes the Eir D1000 Router, Vacron NVR devices, devices using the Realtek SDK (for the CVE-2014-8361 vuln), Netgear R7000 and R6400, DGN1000 Netgear routers, MVPower DVR, Huawei Router HG532 (for CVE-2017-17215), D-Link Devices and GPON Routers.

Netlabs is somewhat vague on mediation. They say to "update the patch in a timely manner, and determine whether they are infected by looking up the process and file name, and HTTP, DHT network connection characteristics created by Mozi Botnet." This seems to mean hand-tweaking of all networks possibly exposed.

As more information about the botnet emerges, tools will no doubt be developed to help in the mediation.

— Larry Loeb has written for many of the last century's major "dead tree" computer magazines, having been, among other things, a consulting editor for BYTE magazine and senior editor for the launch of WebWeek.