A crypto currency thief hijacked traffic that was meant for large hosting companies including Amazon, Digital Ocean, OVH, and others earlier this year in a heist that earned him some $83,000 in profits in more than four months, researchers revealed last week.
Researchers with Dell SecureWorks Counter Threat Unit published the new research on the attacks in conjunction with the Black Hat USA show in Las Vegas. Dell SecureWorks says some 51 networks were compromised from 19 Internet service providers as the thief redirected crypto currency miners to his own mining pool and stole their profits -- to the tune of $9,000 per day. The crypto currency hijack also interrupted network traffic for other users in the netblocks he targeted, the researchers say, but the attacker was mainly interested in the miners.
"They were man-in-the-middle hijacking crypto currency. I found my [account] was hijacked, too," says Joe Stewart, director of malware research for Dell SecureWorks. When Stewart first heard of the crypto currency theft, he figured the attacker had hijacked Border Gateway Protocol (BGP) routes and redirected their mining to the rogue systems. The Internet's BGP routing protocol basically connects networks on the Internet.
It turns out Stewart was correct: The attacker had blasted phony BGP broadcasts that redirected the victims' crypto currency traffic to his server. "He only hijacked it for brief periods where he was able to capture and trap a large section of miners," Stewart says, so the hijack was not necessarily noticeable.
The attacker was successful in part because crypto currency miners employ a protocol called Stratum that has little or no security. "They're not using HTTPS, so any mining pool can send or reconnect to send to a different IP. [The protocol] trusts that they are talking to the real server."
It was that inherent trust that the hijacker capitalized on. But Stewart says the culprit also needed the administrative rights to pull off the BGP spoof, so it was likely an employee or former employee of an ISP. "Or a hacker hacked a router."
The researchers ultimately traced the malicious BGP announcements to a single router at an ISP in Canada. "We reported it to the ISP, and gave them large logs." The activity ultimately came to a halt, he says, and the ISP didn't provide any additional information on its resolution.
Dell SecureWorks' Pat Litke, who worked with Stewart on investigating the theft, says at the heart of the problem is the ISP not having proper oversight of its offending employee or former employee.
But even more unsettling was how the attacker was able to temporarily commandeer all of those IP addresses. The affected hosting providers "have a huge range of IP addresses," says Litke. "The addresses being hijacked were fairly negligible. It didn't impact them… They weren't losing money, and their customers didn't notice."
The only noticeable glitch would be that users wouldn't be able to ping a server, but that would have been seen as a temporary network problem. "Only the miners got trapped for a longer period of time," Stewart says. "We didn't see any big website hijacked in that."
It was when miners started talking online in a Bitcoin forum about lost funds that it become obvious something had gone awry. On March 22, a user named "caution" noted sketchy activity in the wafflepool.com mining pool. Other miners chimed in with similar observations of their mining systems being redirected to an IP address they didn't recognize, and ultimately, their loss of funds.
According to Dell SecureWorks, some $2.6 million in crypto currency mining occurs daily. The researchers suggest that ISPs use the Resource Public Key Infrastructure service, and miners use a Secure Sockets Layer (SSL) client to encrypt their traffic. "Miners should also implement server certificate validation. This validation ensures that the certificate the pool server sends when establishing the connection is valid and authorized for use with the connected domain, even if the domain's IP address changes," the researchers wrote in their report about the attacks.