• Tag Archives Locky
  • Using DNS to weaken Locky ransomware threat

    Ransomware and other cyberthreats often go unseen by traditional detection methods like antivirus, deep packet inspection (DPI) or sandboxing. In fact, a report by Lastline Labs indicates that 51% of zero-day malware—threats that strike before developers have time to release a patch—is undetected by anti-virus solutions. So what can security professionals do to stop attacks? The answer lies, in part, in DNS.

    One of the most powerful ransomware threats currently targeting individuals and organizations is Locky, which infects up to 100,000 devices per day, of which 3% submit payments. Cybersecurity experts estimate that Locky possesses 17% of the entire global market share for all ransomware infections.

    First, let’s look at a few statistics that demonstrate the power and expense of Locky:

    Locky is typically delivered through aggressive spam campaigns, often claiming to be an invoice. Despite the known dangers of clicking on links in unknown emails, Locky is so sly it entices even trained IT staff to click on obscure messages and activate downloads.

    Once a download has completed, Locky connects with its Command & Control (C&C) server to get a cryptographic key to use for encryption. There are three known mechanisms for Locky to reach its C&C hosts:

    1. Direct IP communication
    2. A number of fixed domains
    3. A time-based Domain Generation Algorithm (DGA) that creates a set of random-looking domains that are only valid for a few days

    Here is where DNS can play a role. DNS data can be analyzed to identify C&C connection mechanisms. When these communications are blocked, Locky’s ability to obtain encryption keys is limited, giving infected users a better chance of being protected.

    Unfortunately, the DGA used by Locky to generate domains and get encryption keys is marked with the current time period combined with a secret seed, making it harder to block new domains quickly. Locky changes seeds frequently, and reverse engineering current versions of the malware to discover each new seed takes time. Every new seed indicates another wave in the life of the exploit, so until there is an accurate way to identify traffic associated with Locky, it can’t be permanently blocked.

    But examination of a worldwide feed of anonymized DNS queries, along with anomaly detection and correlation technology, makes it possible to identify suspected domains used by Locky to download encryption keys in real time. ForcePoint is one company that has done some work to reverse engineer the DGA used by Locky. By using the existing DGA and conducting some additional processing of suspect domains, it is possible to determine new seeds used by Locky, thereby enumerating all future new domains Locky will use.

    Below is a sampling of more recent domains created by Locky as detected by our DNS algorithms:

    • mrjuvawlwa[.]xyz
    • uydvrqwgg[.]su
    • uwiyklntlxpxj[.]work
    • owvtbqledaraqq[.]su
    • udfaexci[.]ru
    • eabfhwl[.]ru
    • olyedawaki[.]pl
    • uxwfukfqxhydqawmf[.]su
    • ikdcjjcyjtpsc[.]work
    • wrbwtvcv[.]su
    • osxbymbjwuotd[.]click
    • qtuanjdpx[.]info

    As Locky and other types of ransomware become more adept at avoiding detection and remediation, new strategies need to be used to combat them. Many of the new cyberthreat strategies make traditional malware block lists less effective. Facing DGAs with fast-changing seeds, security researchers must constantly identify the new seeds used by each wave of phishing to pre-generate domains. Once new seeds are released the old ones immediately become obsolete.

    By utilizing a broad set of DNS query data, it is possible to detect and track the evolution of generated domains through a variety of algorithmic methods such as clustering, reputation scoring, reverse engineering and additional methods that continuously evolve. Recent innovations include anomaly detection algorithms, new domain clustering and a Domain Reputation System that resulted in almost 100,000 domains and C&Cs provisioned daily for blocking.

    By employing these advanced methods, suspicious domains can be detected with a high level of accuracy very quickly, and false positives can also be weeded out so good traffic can still reach legitimate sites. Currently, this is the best defense against Locky. Service providers and companies can use this technique to protect their online users from having their files encrypted, and identify machines that have been infected.

    Locky provides ample evidence that attackers are continuously innovating. Staying one step ahead requires cybersecurity expertise and real-time processing of massive, worldwide data sets to uncover malicious activity. Blocking traffic to these domains is a good way to avoid the threat of Locky, and expert security teams that take the right steps to understand its behavior and put appropriate measures in place to protect would-be victims will render cyberthreats much less effective.


  • New Spam Campaign Distributes Locky Ransomware and Kovter Trojan Combined

    Criminals have taken a liking to the idea of combining multiple types of malware into one distribution campaign. Malware Protection Center researchers discovered a string of email messages using malicious attachments to spread both Locky ransomware and the Kovter Trojan. It is not the first time these two types of malware are distributed in the same campaign, as dual-pronged spam campaigns have become more common as of late.

    This morning we noticed the start of a campaign using  New notice to Appear in Court as the email subject. The attachments are identical to the Typical .JS, .WSF, .lnk file inside a double zip. All the sites seen so far today are the same sites used in the USPS, FedEx, UPS current campaigns.  I am sure that both campaigns will continue side by side. It is very likely that different “affiliates” are using the same distribution network, but each one prefers a different email lure to gain victims.

    The attachments all start with a zip named along the lines of Notice_00790613.zip which contain another zip Notice_00790613.doc.zip which in turn contains Notice_00790613.doc.js

    Criminals Step Up Malware Distribution

    It is rather disconcerting to learn opening a malicious email attachment can introduce two different types of malware at the same time. As if the Locky ransomware is not annoying to deal with on its own, computer users will also be affected by the Kovter Trojan. This latter piece of malware specialized in click fraud, generating a lot of illegal advertisement revenue for criminals.

    Through a malicious email attachment, criminals execute a script that contains links to multiple domains where the malware types are downloaded from. By making the attachment a .Ink file, the recipient may click it and have the payload download executed in the background. PowerShell scripts have become a fan favorite among criminals targeting Windows users these days, that much is certain.

    Researchers discovered a total of five hardcoded domains in the script from where the malware can be downloaded. Both the Locky ransomware and Kovter Trojan payloads are hosted on these platforms, and it is expected more of these domains will continue to pop up over time. Although law enforcement agencies can take down these domains rather easily, criminals will not hesitate to create additional hosting solutions over time.

    As one would expect from these spam email campaigns, the message in question is a fake receipt for a spoofed USPS delivery email. In the attached zip file, there is the malicious .Ink file , which initiates the PowerShell script once opened. One interesting aspect about this script is how it checks if the file is downloaded successfully and if is at least 10KB in size. Once that has been verified, it will stop the process automatically.

    Microsoft researchers feel the use of multiple domain names to download the payload from is a powerful obfuscation technique. Blacklisting one specific URL is a lot easier than dealing with a handful of different domains. Moreover, this method seems to hint at how criminals can easily add more servers to download the malicious payloads from if they want to. A very troublesome development, to say the least.

    Perhaps the most worrisome aspect of this new malware distribution campaign is how criminals continue to update the payloads themselves. Both Kovter and Locky receive regular updates, which means the development of ransomware and click-fraud Trojans is still going on behind the scenes. Moreover, it goes to show criminals will continue to rely on multi-pronged distribution campaigns for malware and ransomware moving forward.