Locky ransomware may be a relatively new threat for IT security professionals to worry about, but it has not taken long for the malicious malware to make its mark. It has already claimed a number of high profile victims and is fast becoming one of the most prevalent forms of ransomware.
Early last month Hollywood Presbyterian Hospital in California experienced a ransomware attack that took some of its systems out of action for a week until a ransom demand of $17,000 was paid and the hospital’s EHR was decrypted. During that week, staff at the hospital were forced to record data on paper, were unable to check medical records, and X-Ray, CT scans and other medical imaging files were inaccessible. The hospital was not targeted, instead it was the victim of a random attack. That attack was linked to Locky ransomware.
Locky Ransomware Capable of Encrypting Files Stored on Network Drives
Locky ransomware infections occur via spam email messages and it appears that Hollywood Presbyterian hospital’s systems were infected via an email campaign. Locky ransomware is not delivered via spam email directly, instead infection occurs via a malicious Word macro.
When the macro is run, the malicious code saves a file to the disk and downloads the ransomware from a remote server. Upon download the malware searches for a range of file types located on the device on which it is saved, as well as searching portable drives, virtual devices, and network drives to which the computer is connected. Volume Snapshot Service (VSS) files are also removed, removing the option of restoring via Windows backup files.
Staff training on malicious file detection often covers common file types used to mask malicious software such as screensaver files (SCR), executables (EXE), and batch files (BAT). In the case of Locky ransomware, users are more likely to be fooled as infections occur as a result of Word document (DOC) macros. Any user who receives and opens an infected Word document will automatically download Locky to their computer if they have macros set to run automatically. Since users are instructed to enable macros upon opening the infected document, many may do so in order to read the contents of the file.
According to Trustwave SpiderLabs, 18% of the spam emails it had collected over the course of the past week were ransomware, and Locky is believed to comprise a large percentage of those emails. The ransomware is being delivered by the same botnet that was used to send out Dridex malware last year. While the mastermind behind the Dridex banking malware, Moldovan Andrey Ghinkul, has now been apprehended and extradited to the U.S, the botnet infrastructure is being used for this much simpler attack.
The attacks may be simpler but they are providing to be effective. According to Fortinet, over three million hits have been recorded from the Command and Control server used to communicate with Locky.
The infections are unlikely to end until the botnet is taken down. In the meantime, it is essential to exercise caution. While the ransomware does not attack Russian systems, all other users are at risk. Businesses in particular should take action to reduce risk, such as advising staff of the threat of infection via Word files and Zip files. Using a spam filtering solution such as SpamTitan to block malicious attachments is also strongly advisable to prevent malicious emails from being delivered to staff inboxes.