A new strain of the Glupteba malware is cashing in on bitcoin transactions to continually update command-and-control (C&C) servers.
Discovered in 2011, the Glupteba Trojan has been used in multiple exploit kit attacks. Now, Trend Micro has identified a new strain that contains a browser stealer for sensitive data and a routine exploiter for MikroTik routers via the CVE-2018-14847 vulnerability. This version also contains a unique approach to updating its C&C servers: bitcoin transactions.
Using Blockchain to Update C&C Servers
Cutting links to C&C servers is an effective way to blunt the impact of malware infections. If malicious code strains can’t connect with data destinations, they often suspend operations or are rendered inert. As noted by The Next Web, however, the latest strain of Glupteba malware takes a new approach to continual connection by leveraging blockchain.
First, attackers use the Electrum bitcoin wallet to complete small transactions. These transactions include OP_RETURN data that contains encrypted C&C domain information. When Glupteba is activated on compromised devices, it uses a hardcoded ScriptHash string to seek out and decrypt this return data. This technique allows cybercriminals to sidestep typical security measures. If server links are severed, attackers simply make another bitcoin transaction to supply malware with a fresh C&C address.
A Range of Malicious Capabilities
While strains of Glupteba were often found as part of exploit kits, Bleeping Computer pointed out that the newest version relies on malvertising to force a dropper download and flood targets with multiple malware variants that enable malicious actors to download and execute files, take screenshots, compromise routers and turn infected devices into XMR mining machines.
In addition, the malware attempts to gain increased control over device functions by elevating privileges via the fodhelper method — fodhelper.exe naturally runs with high integrity, allowing attackers to bypass User Account Control (UAC) using custom registry entries — or identifying itself as a SYSTEM user by using stolen winlogon process tokens.
Breaking the Chain
Malicious emails and links are the top infection vector for malware threats such as Glupteba. Regular router patching is critical to avoid CVE-2018-14847 and similar vulnerabilities.
When it comes to the use of blockchain to deliver C&C addresses, IBM experts note that its nature — blockchain is code, and code can be flawed — combined with a dearth of industry expertise opens potential avenues of compromise. Breaking the chain demands both broad cloud security controls to manage transactions at scale and specific user identity oversight to limit the risk of accidental exposure.