This post was authored by Edmund Brumaghin and Colin Grady
The Domain Name System (DNS) is one of the most commonly used Internet application protocols on corporate networks. It is responsible for providing name resolution so that network resources can be accessed by name, rather than requiring users to memorize IP addresses. While many organizations implement strict egress filtering as it pertains to web traffic, firewall rules, etc. many have less stringent controls in place to protect against DNS based threats. Attackers have recognized this and commonly encapsulate different network protocols within DNS to evade security devices.
Typically this use of DNS is related to the exfiltration of information. Talos recently analyzed an interesting malware sample that made use of DNS TXT record queries and responses to create a bidirectional Command and Control (C2) channel. This allows the attacker to use DNS communications to submit new commands to be run on infected machines and return the results of the command execution to the attacker. This is an extremely uncommon and evasive way of administering a RAT. The use of multiple stages of Powershell with various stages being completely fileless indicates an attacker who has taken significant measures to avoid detection.
Ironically, the author of the malware called SourceFire out in the malware code itself shortly after we released Cisco Umbrella, a security product specifically designed to protect organizations from DNS and web based threats as described here.
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This Post Authored by Nick Biasini
UPDATE: It was recently disclosed that in addition to Content-Type being vulnerable, both Content-Disposition and Content-Length can be manipulated to trigger this particular vulnerability. No new CVE was listed, however details of the vulnerability and remediation are available in this security advisory.
Talos has observed a new Apache vulnerability that is being actively exploited in the wild. The vulnerability (CVE-2017-5638) is a remote code execution bug that affects the Jakarta Multipart parser in Apache Struts, referenced in this security advisory. Talos began investigating for exploitation attempts and found a high number of exploitation events. The majority of the exploitation attempts seem to be leveraging a publicly released PoC that is being used to run various commands. Talos has observed simple commands (i.e. whoami) as well as more sophisticated commands including pulling down a malicious ELF executable and execution.
With exploitation actively underway Talos recommends immediate upgrading if possible or following the work around referenced in the above security advisory.
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As a reminder, the information provided for the following threats in this post is non-exhaustive and current as of date of publication. Detection and coverage for the following threats is subject to updates pending additional threat or vulnerability analysis. For the most current information, please refer to your FireSIGHT Management Center, Snort.org, or ClamAV.net.
Ransomware continues to be a plague on the internet and still sets itself as the fastest growing malware family we have seen in the last number of years. In this post we describe the technical details about a newly observed campaign of the notorious Crypt0l0cker (aka TorrentLocker or Teerac) ransomware. Crypt0l0cker has gone through a long evolution, the adversaries are updating and improving the malware on a regular basis. Several indicators inside the samples we have analysed point to a new major version of the malware. We have already seen large campaigns targeting Europe and other parts of the world in 2014 and 2015. It seems to be that the actors behind these campaigns are back now and launching again massive spam attacks. This post will also give you insights about the level of sophistication this malware has reached.