NotPetya ransomware attacks have spread globally, with the latest figures from Microsoft suggesting there are now more than 12,500 reported victims spread across 65 countries. The attacks first started to be reported on Tuesday morning with companies in the Ukraine hit particularly hard.
At first it appeared that the attacks involved Petya ransomware, although it has since been confirmed that this is a new ransomware variant. The ransomware has already attracted a variety of names such as GoldenEye, SortaPetya, ExPetr, and NotPetya. We shall use the latter.
Security researchers believe the NotPetya ransomware attacks started in Ukraine. The first attacks occurred the day before a national holiday – a common time to launch an attack. IT staff were unlikely to be working, so the probability of the attacks being halted before the ransomware was allowed to run would be increased.
The NotPetya ransomware attacks have been discovered to have occurred via a variety of vectors. Ukraine was hit particularly hard, which suggested a country-specific attack vector. Some security researchers have suggested the first attacks occurred via a Ukrainian accounting package called M.E. Doc, with the attackers managing to compromise a software update. M.E.Doc hinted that this may be the case initially, but later denied they were the cause of the attack. If it is true that a software update was involved, it would not be the first time M.E.Doc was attacked. A similar ransomware attack occurred via M.E.Doc software updates in May.
However, that is only one potential attack vector used in the NotPetya ransomware attacks. It has been confirmed that the attackers are also using two NSA exploits that were released by Shadow Brokers in April. As was the case with the WannaCry ransomware attacks, the EternalBlue exploit is being used. The latest attacks are also using another exploit released at the same time called EternalRomance.
In contrast to the WannaCry ransomware attacks last month, the exploits used in the NotPetya ransomware attacks only scan for vulnerable devices on local networks, not via the Internet.
Both exploits will not work if computers have already been patched with MS17-010 released by Microsoft in March. Following the WannaCry attacks, Microsoft also issued a patch for older, unsupported Windows versions to prevent further ransomware attacks.
However, patching would not necessarily have prevented infection. In contrast to WannaCry, NotPetya ransomware attacks have been reported by companies that have patched their computers. Security researchers have confirmed that all it takes for infection to occur is for one computer to have been missed when applying the patches. That allows the attackers to attack that machine, and also any other machines connected to the local network, even if the patch has been applied.
The attacks also appear to be occurring via phishing emails containing malicious Microsoft Office documents. As has been the case with many other ransomware attacks, the failure to implement spam defenses can result in infection. The use of an advanced spam filter such as SpamTitan offers excellent protection against email-based ransomware attacks, preventing those emails from reaching end users’ inboxes.
Upon infection, the ransomware waits one hour before executing and forcing a reboot. When the computer restarts, the ransom note appears. The ransom demand is for $300 per infected machine. In contrast to the majority of ransomware variants, NotPetya does not encrypt files. Instead it replaces the Master File Table (MFT). Since the MFT shows the computer where files are located on the hard drive, without it files cannot be found. Files are not encrypted, but they still cannot be accessed.
Preventing ransomware attacks such as this requires regular patching to address vulnerabilities and anti-spam solutions to prevent malicious emails from being delivered.
Fortunately, NotPetya ransomware attacks can be blocked. Cybereason security researcher Amit Serber has found a way to vaccinate computers against this specific ransomware variant. He suggests IT teams “Create a file called perfc in the C:\Windows folder and make it read only.” This method has been confirmed as effective by other security researchers, although it will not work if infection has already occurred.
Unfortunately, recovery following an attack may not be possible if infected computers cannot be restored from backups. Kaspersky Lab reports there is a flaw in the ransomware saying, “We have analyzed the high level code of the encryption routine and we have figured out that after disk encryption, the threat actor could not decrypt victims’ disks.” Further, the email account used by the attacker to verify ransom payments has been shut down by a German email provider.