In the tech world recently there have been discussions regarding a new type of ransomware, which has been dubbed “PowerWare”. It has been named this way due to the fact that instead of using an exploit to download malicious software to run on the users’ machine and encrypt their files, exploits are instead used to invoke PowerShell to do the damage.

The mechanism is very similar to previous malware attempts delivered via exploited documents – a good example being a malicious macro in a Microsoft Word document that spawns cmd.exe, which in turn opens two instances of PowerShell; one to download a malicious script, and the other to run the script once the download is complete.

You can appreciate why this has been done; it’s much easier for malware to execute when PowerShell is viewed as a piece of legitimate software that is needed day to day to run scripts or cmdlets in your environment. The difficulty is finding a way to ensure that this cannot access your users’ files.

Many implementations would use heuristics in order to detect malicious behaviour; others may block PowerShell or cmd in certain circumstances, such as when it is a child process of a potentially malicious source, e.g. Microsoft Word, or Adobe Reader. However this is limited by trying to blacklist all possible attack types; any gaps would allow attacks to work out a way around the restrictions.

Using Defendpoint, you can proactively defend against this type of malware. In the PowerWare scenario, the user either downloads the malicious document via the web browser, or receives the document via a phishing email. Defendpoint automatically isolates the document in a secure Sandbox. The Sandbox is isolated from the user environment, so it is straight forward to apply strict application whitelisting; only the browser, plugins and content viewers should run. This can not only prevent the attacker from launching PowerShell, but prevents any malicious applications or scripts dropped to disk from executing as well.

The unique context of the Sandbox allows Defendpoint to block web-based threats that exploit tools such as PowerShell, without limiting the user's ability to launch them. As Defendpoint is completely proactive, it is just as effective against any other future attacks, as well as current known ones, that makes use of malicious content in this manner.