Interestingly, and in what appears to be a growing trend, the latest Redman version hides the dynamic IP address of its C&C server by converting each octet of the IP address from decimal to hexadecimal:, e.g. 184.108.40.206 => B9.CB.74.2F, scrambling the latter, then hiding it in the form of a small payment to their own Bitcoin wallet.
To reveal the C&C address, Redaman send a GET request to get the last ten transactions on the hard coded Bitcoin wallet; it takes the values of the last two payment transactions to Bitcoin wallets, converts the Decimal values from the transactions to Hexadecimal; splits the Hexadecimal value to low and high bytes, changes the order and converts them back to decimal; these values together combine the IP address of the hidden C&C server.
The malware’s not the first to use Blockchain to hide C&C infrastructure: Trend Micro researchers identified the Glupteba malware as also updating its C&C server address through the blockchain via the function discoverDomain.
As they noted in September: “The discoverDomain function can be run either by sending a backdoor command, or automatically by the dropper. DiscoverDomain first enumerates Electrum Bitcoin wallet servers using a publicly available list, then tries to query the blockchain script hash history of the script with a hardcoded hash.”
In most other respects Redaman, meanwhile, is a typical banking trojan.
Checkpoint warns users to look out for Bitcoin wallet 1BkeGqpo8M5KNVYXW3obmQt1R58zXAqLBQ, which is “not recognised as malicious in any blockchain databases”.
This article is from the CBROnline archive: some formatting and images may not be present.
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