Locky ransomware has already affected thousands of users. Unfortunately, the threat is not nearly done with its infections, as new, more dangerous methods of distribution were just reported by security researchers at TrendMicro.
The new techniques include the already known deployment of the Flash zero-day exploit CVE-2016-1019 (used in Locky’s earlier drive-by download attacks) and an escalation of privileges exploit in Windows – CVE-2015-1701. This exploit was used to bypass sandbox technologies.
|Short Description||The infamous Locky ransomware has employed new distribution and infection techniques.|
|Symptoms||The user’s files are encrypted and a ransom is demanded.|
|Distribution Method||A Flash exploit and a kernel-level faws are leveraged.|
|Detection Tool||Download Malware Removal Tool, to See If Your System Has Been Affected by Locky Ransomware|
|User Experience||Join our forum to discuss Locky Ransomware.|
CVE-2015-1701 Official Description
Win32k.sys in the kernel-mode drivers in Microsoft Windows Server 2003 SP2, Vista SP2, and Server 2008 SP2 allows local users to gain privileges via a crafted application, as exploited in the wild in April 2015, aka “Win32k Elevation of Privilege Vulnerability”.
Analysis of the Attack
One of the discoveries of TrendMicro’s research is a downloader file detected as TROJ_LOCKY.DLDRA. The researchers also captured network traffic and found a steady use of the Flash exploit mentioned in the beginning.
Learn More about Locky Ransomware
Further Analysts of TROJ_LOCKY.DLDRA
TROJ_LOCKY.DLDRA, on the other hand, used the kernel exploit. The downloader was detected to connect to a Command & Control server located at 202[.]102[.]110[.]204:80. It also installed Locky. The interesting part is that the whole procedure would need several kernel-level instruments:
- Work items;
- System threads;
- Asynchronous procedure calls, or APC.
All the above don’t need any files to be created, and as a result, Locky can be installed directly onto a system, evading detection. As with many other malware files, Locky’s downloader uses svchost.exe.
Researchers believe that CVE-2015-1701 kernel-level exploit s used to avoid detection by security vendors and conceal its malicious behavior. The exploit makes the whole infection process more complex and more difficult for sandboxing detection and analysis. Furthermore, other kernel exploits may also be used for later versions of Windows OS.
The malware sample analyzed by TrendMicro’s research team also has various anti-debug tricks and a new packing method, such as decrypted API strings and construction of API addresses at run time.
After the activation of the kernel flaw, the downloader file will handle other techniques to conceal its bad behavior. Overall, the attack is quite complicated and to understand it, you should have above average knowledge of the inner workings of Windows and malicious software.
Is There an Antidote for Locky’s Latest Infection?
Researchers believe that the success of this latest attack is due to the fact that not many people pay attention to kernel exploits. Furthermore, the above-mentioned work items, APCs, and system threads are typically not monitored for malicious behavior. Not only are they disregarded but also monitoring them would be a tough job.
However, the deployment of sxchost.exe is a typical malware routine and is perfect for concealing network traffic.
What should you do to prevent the attack from happening? The very first thing you should do is update your system with the latest version of Adobe Flash. If you’re having difficulties monitoring and updating your software, you can rely on a software inspector program such as Secunia:
To add another layer of protection, consider installing an anti-ransomware utility, such as the ones described in the article below. However, keep in mind that most tools only protect against particular ransomware families.
Another thing you should immediately do is backup all of your data.
If it’s too late and you have already been infected with Locky, have a look at the manual below.