Security firm Cyren issued a new report, “Botnets: The Clone Army of Cybercrime,” that described a new method of circumventing security blocking efforts. The researchers referred to this evasive technique as a “ghost host.”

Ghost Host in the Machine

SecurityWeek noted that, to carry out the procedure, malware authors place unknown host names in the HTTP host fields of a botnet’s communications. These host names can be registered and unregistered. Because of the indeterminate state of the included host names, which may or may not resolve in the Domain Name System (DNS), this can easily fool usual web security and URL-filtering systems.

The total IP range associated with a bad URL is not usually blocked because legitimate domains may also exist at the IP. Blocking the entire IP would block those legitimate domains.

The impetus for this discovery originated when Cyren detected communications between bot and server even after it blocked the malware server’s URL in the filters protecting a system. It noticed that a botnet member informed the command-and-control (C&C) server that a new infection had occurred. The researchers said they were unsure just how this communication took place at all.

Playing the Name Game

While the destination IP address of the communication packet was still known to be a bad server, the HTTP host fields that were used for requests were assigned to completely different domains. These domains are stuffed into the host fields that Cyren referred to as ghost hosts.

In one case, the researchers noted, the fake domains were “” and “” The resolved domains were blocked, but not the ghost hosts. Changing the ghost host name sent in a communication might prompt different response actions from the C&C server. One host might document a new addition to the botnet, but another ghost name could serve new exploit code.

This is a novel technique that establishes a side-channel communication with a malware’s C&C server, survives a primary blacklist and delivers a resiliency that could impact the overall malware landscape. The increase in resiliency that it brings to malware will have to be evaluated in the near future.

More from

Most organizations want security vendor consolidation

4 min read - Cybersecurity is complicated, to say the least. Maintaining a strong security posture goes far beyond knowing about attack groups and their devious TTPs. Merely understanding, coordinating and unifying security tools can be challenging.We quickly passed through the “not if, but when” stage of cyberattacks. Now, it’s commonplace for companies to have experienced multiple breaches. Today, cybersecurity has taken a seat in core business strategy discussions as the risks and costs have risen dramatically.For this reason, 75% of organizations seek to…

How IBM secures the U.S. Open

2 min read - More than 15 million tennis fans around the world visited the US Open app and website this year, checking scores, poring over statistics and watching highlights from hundreds of matches over the two weeks of the tournament. To help develop this world-class digital experience, IBM Consulting worked closely with the USTA, developing powerful generative AI models that transform tennis data into insights and original content. Using IBM watsonx, a next-generation AI and data platform, the team built and managed the entire…

How the FBI Fights Back Against Worldwide Cyberattacks

5 min read - In the worldwide battle against malicious cyberattacks, there is no organization more central to the fight than the Federal Bureau of Investigation (FBI). And recent years have proven that the bureau still has some surprises up its sleeve. In early May, the U.S. Department of Justice announced the conclusion of a U.S. government operation called MEDUSA. The operation disrupted a global peer-to-peer network of computers compromised by malware called Snake. Attributed to a unit of the Russian government Security Service,…

How NIST Cybersecurity Framework 2.0 Tackles Risk Management

4 min read - The NIST Cybersecurity Framework 2.0 (CSF) is moving into its final stages before its 2024 implementation. After the public discussion period to inform decisions for the framework closed in May, it’s time to learn more about what to expect from the changes to the guidelines. The updated CSF is being aligned with the Biden Administration’s National Cybersecurity Strategy, according to Cherilyn Pascoe, senior technology policy advisor with NIST, at the 2023 RSA Conference. This sets up the new CSF to…