The recent Petya cyber security attack does not follow other recent attacks.

The recent Petya cyber security attack does not follow other recent attacks.

Security researchers are struggling to reach consensus on whether the ransomware responsible for the latest global attacks is a new version of Petya or not, and even whether it was true ransomware, but what they have learned so far could help guide security strategies.

Those in support of retaining the Petya name point out that it essentially behaves in exactly the same way because it is designed to:

Encrypt files on disk without changing the file extension.
Forcibly reboot the machine upon infection.
Encrypt the Master Boot Record on affected machines.
Present a fake CHKDSK screen as a cover for the encryption process.
Present a near-identical ransom demand screen after completing its activities.

According to the latest update on the malware, Kaspersky Lab says code analysis has revealed it is technically impossible to decrypt victims’ disks.

To decrypt a victim’s disk threat actors need the installation ID, and in previous versions of “similar” ransomware like Petya/Mischa/GoldenEye, this installation ID contained the information necessary for key recovery, researchers at the security firm said.

However, they found the new malware – which they have dubbed ExPetr – does not have any such recovery mechanism, which means the threat actor could not extract the necessary information needed for decryption.

In short, victims could not recover their data even if they paid the ransom, the researchers said, which again calls into question the motive behind the malware.

This discovery not only further endorses the security community’s earlier advice not to pay the ransom, but also raises further questions about the true purpose of the malware and is likely to fuel further speculation that it may have been intended purely as a means to cause disruption on to mask some other malicious activity.

This view is supported by the latest statement from the UK National Cyber Security Centre (NCSC) that while managing the impact to the UK of the incident, the NCSC’s experts have found evidence that questions initial judgements that the intention was to collect a ransom. “We are investigating with the NCA and industry whether the intent was to disrupt rather than for any financial gain,” the NCSC said.

Whatever the true purpose, analysis of the malware has confirmed some of the lessons learned from WannaCry and added others which organisations should consider in order to improve their cyber defence capabilities against future threats.

The key lessons from the cyber security attack that have emerged so far are:

1. Having the latest versions of software and ensuring they are patched up to date will go a long way in reducing organisations’ vulnerability to cyber attack.

2. Malware is increasingly using legitimate tools for malicious activity to go undetected. In the case of ExPetr, two common Windows administrative tools, Windows Management Instrumentation Command-line (WMIC) and PsExec were used.

3. Malware is hijacking software updating mechanisms to spread malware, and is likely to use this technique increasingly in future.

4. An appropriate and well-tested backup and recovery plan for critical systems and data will go a long way to mitigating the effects of ransomware and other malware attacks, regardless of its particular characteristics.

5. Malware is abusing security tools to discover usernames and passwords, which means organisations should ensure they have appropriate systems and procedures in place to prevent credential abuse.

ExPetr uses the publically available Mimikatz tool to obtain credentials of all Windows users in plaintext, including local administrators and domain users to spread itself on local networks. You can find more details at: https://github.com/gentilkiwi/mimikatz

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