This post was authored by Nick Biasini
Over the last six months the exploit kit landscape has seen some major changes. These changes began with Nuclear ceasing operations in April/May and arrests in Russia coinciding with the end of Angler in June. Recently, Neutrino has been added to the list of exploit kits that have stopped being actively used in 2016. What remains is a group of smaller exploit kits vying for pole position in an industry that continues to generate millions of dollars from payloads such as ransomware and banking trojans.
It’s now time to turn to another exploit kit that is active on the landscape, Sundown. The Sundown exploit kit has previously been part of a second tier of exploit kits that includes Magnitude and Sweet Orange. These kits successfully compromise users, but typically are not accompanied with the advanced techniques and wide-spread use of the other major exploit kits. It’s not to say these kits aren’t significant threats, but from a potential victim perspective they historically do not have the reach associated with other EKs from before such as Angler or RIG.
These Vulnerabilities were discovered by Tyler Bohan of Cisco Talos.
Talos is releasing multiple vulnerabilities (TALOS-2016-0187, TALOS-2016-0190 & TALOS-2016-0205) in the LibTIFF library . One vulnerability (TALOS-2016-0187) is an exploitable heap based buffer overflow that impacts the LibTIFF TIFF2PDF conversion tool. Another vulnerability (TALOS-2016-0190) impacts the parsing and handling of TIFF images ultimately leading to remote code execution. The final vulnerability (TALOS-2016-0205) is an exploitable heap based buffer overflow in the handling of compressed TIFF images in LibTIFF’s PixarLogDecode API. An attacker who can trick a user into processing a malformed TIFF document can use one of these vulnerabilities to achieve remote code execution on the targeted system.
The Tagged Image File Format (TIFF) was developed in the mid-1980’s as a common file format able to store image data in a lossless format for the burgeoning image manipulation industry. Since then TIFF files have been widely adopted within the graphic arts industry, and also by electronic fax systems.
We had .locky, we had .odin and then we had .zepto but today we hit rock bottom and we now have Locky using .shit as their encrypted file extension. In today’s latest wave of spam, Talos has observed three distinct spam campaigns distributing the newest version of Locky ransomware. This comes after a seeming vacation for Locky for around two weeks. Using the LockyDump utility that was previously released by Talos, we were able to determine that there are distinct differences in the characteristics of the malware campaigns that seem to correlate with the Affiliate ID associated with the Locky binaries that are delivered by each campaign.
The technical details associated with the Locky ransomware family itself has been extensively documented and reported on, so we won’t spend time providing an in-depth technical analysis of the ransomware family itself. This post highlights some of the distinct characteristics that we have observed for each campaign. We will summarize all Indicators of Compromise (IOCs) at the end of this post.
This post was authored by Edmund Brumaghin and Yves Younan
Ransomware has become increasingly prevalent in the industry, and in many cases, unless there is a publicly released decryptor available, there is often not an easy means of retrieving encrypted files once a system has been infected. In addition to the creation and maintenance of regular system backups, it is increasingly important to focus on a multi-tiered defense-in-depth network architecture in an effort to prevent initial endpoint infection. This is often difficult in an evolving threat landscape where new ransomware families are being developed and deployed seemingly every day by threat actors of varying levels of sophistication.
While many ransomware families focus on the encryption of all or portions of a target system’s files others, such as Petya, rely on overwriting the contents of the Master Boot Record (MBR) to force a system reboot then only encrypt the Master File Table (MFT) of the hard drive on infected systems as a way to coerce users into paying the threat actors to retrieve the encryption keys required to decrypt their files.
To help combat ransomware that attempts to modify the MBR, Talos has released a new tool to the open source community, MBRFilter, a driver that allows the MBR to be placed into a read-only mode, preventing malicious software from writing to or modifying the contents of this section of the storage device.
Vulnerability Discovered by Tyler Bohan and Cory Duplantis of Cisco Talos
Talos has identified an exploitable out-of-bounds write vulnerability in the ELF Section Header parsing functionality of Hopper (TALOS-2016-0222/CVE-2016-8390). Hopper is a reverse engineering tool for macOS and Linux allowing the user to disassemble and decompile 32/64bit Intel-based Mac, Linux, Windows and iOS executables. During the parsing of ELF section headers, there is a user controlled size that is not validated, a malicious threat actor could craft an ELF file with specific section headers to trigger this vulnerability, potentially leading to remote code execution. A malicious threat actor could use a zip file containing the crafted executable to target threat researchers, sent via phishing or file sharing sites. This type of exploit can also be used as an anti-analysis measure in an attempt to defeat sandboxes and automated disassembly.
Hopper has been updated the changelog can be read at this URL: https://www.hopperapp.com/rss/html_changelog_v3.php
Vulnerability discovered by Aleksandar Nikolic of Talos.
Talos has identified an information disclosure vulnerability in Foxit PDF Reader (TALOS-2016-0201/CVE-2016-8334). A wrongly bounded call to `memcpy`, while parsing jbig2 segments within a PDF file, can be triggered in Foxit PDF Reader causing an out-of-bounds heap memory to be read into a buffer. The `memcpy` call is properly sized, but the source is smaller than the size argument, causing the adjacent memory to be copied into a buffer, where heap metadata, addresses and pointers can be copied and later reused, disclosing memory layout. Combined with another vulnerability, this information disclosure can be used to leak heap memory layout and bypass ASLR. Phishing campaigns commonly use PDF files, as malicious attachments or linked downloads, to deliver malware.