On Friday, May 12, attackers spread a massive ransomware attack worldwide using the EternalBlue exploit to rapidly propagate the malware over corporate LANs and wireless networks. EternalBlue, originally exposed on April 14 as part of the Shadow Brokers dump of NSA hacking tools, leverages a vulnerability (MS17-010) in Microsoft Server Message Block (SMB) on TCP port 445 to discover vulnerable computers on a network and laterally spread malicious payloads of the attacker’s choice. This particular attack also appeared to use an NSA backdoor called DoublePulsar to actually install the ransomware known as WannaCry.
Over the subsequent weekend, however, we discovered another very large-scale attack using both EternalBlue and DoublePulsar to install the cryptocurrency miner Adylkuzz. Initial statistics suggest that this attack may be larger in scale than WannaCry: because this attack shuts down SMB networking to prevent further infections with other malware (including the WannaCry worm) via that same vulnerability, it may have in fact limited the spread of last week’s WannaCry infection.
Symptoms of this attack include loss of access to shared Windows resources and degradation of PC and server performance. Several large organizations reported network issues this morning that were originally attributed to the WannaCry campaign. However, because of the lack of ransom notices, we now believe that these problems might be associated with Adylkuzz activity. However, it should be noted that the Adylkuzz campaign significantly predates the WannaCry attack, beginning at least on May 2 and possibly as early as April 24. This attack is ongoing and, while less flashy than WannaCry, is nonetheless quite large and potentially quite disruptive.