When hackers corral infected computers into a botnet, they take special care to ensure they don’t lose control of the server that sends commands and updates to the compromised devices. The precautions are designed to thwart security defenders who routinely dismantle botnets by taking over the command-and-control server that administers them in a process known as sinkholing.

Recently, a botnet that researchers have been following for about two years began using a new way to prevent command-and-control server takedowns: by camouflaging one of its IP addresses in the bitcoin blockchain.

Impossible to block, censor, or take down

When things are working normally, infected machines will report to the hardwired control server to receive instructions and malware updates. In the event that server gets sinkholed, however, the botnet will find the IP address for the backup server encoded in the bitcoin blockchain, a decentralized ledger that tracks all transactions made using the digital currency.