The Australian Cyber Security Centre uploaded a number of malware samples found on the systems attacked to VirusTotal, among which was at least one Web shell, according to former NSA hacker Jake Williams, who worked with the agency's elite Tailored Access Operations group (which was disbanded in 2016 and absorbed into the agency’s new Directorate of Operations).
Re this - several recent big attacks (Equifax, Oz Parliament etc) have used web shells. Very easy to deploy, very poor anti-malware control coverage. One to look out for. https://t.co/ORUh90miNQ— Kevin Beaumont (@GossiTheDog) February 18, 2019
VirusTotal, which is owned by Google, supports a large number of scanning engines. Researchers upload malware samples they discover to see if they can be detected by any of the scanning engines as the first step to identifying the malware in question.
The Parliament hack was disclosed on 8 February. On Monday, Prime Minister Scott Morrison told Parliament that the networks of the Liberal, National and Labor Parties had also been attacked.
The samples have either not been detected by the engines on VirusTotal or else have been detected by just one out of more than 60.
Williams said this meant the attackers had been using obfuscation frameworks to get around the detection engines.
"[They are] likely deploying the specific build of the malware in one location," he said.
According to the US-CERT, Web shells are used for the following purposes:
- To harvest and exfiltrate sensitive data and credentials;
- To upload additional malware for the potential of creating, for example, a watering hole for infection and scanning of further victims;
- To use as a relay point to issue commands to hosts inside the network without direct Internet access;
- To use as command-and-control infrastructure, potentially in the form of a bot in a botnet or in support of compromises to additional external networks. This could occur if the adversary intends to maintain long-term persistence.
- While a web shell itself would not normally be used for denial of service attacks, it can act as a platform for uploading further tools, including DoS capability.