Decoding malware via simple statistical analysis

Intro Analyzing malware often requires code reverse engineering which can scare people away from malware analysis. Executables are often encoded to avoid detection. For example, many malicious Word documents have an embedded executable payload that is base64 encoded (or some other encoding). To understand the encoding, and be able to decode the payload for further … Continue reading Decoding malware via simple statistical analysis

Recovering custom hashes for the Petya/Notpetya malware

During our malware analysis, we often come across samples that contain (custom) hashes in stead of cleartext. Hashing is done in an effort to bypass detection and hinder malware analysts. There are tools to recover cleartext from known hashing methods (like John the Ripper and hashcat). But for custom hashing methods, you'll have to write … Continue reading Recovering custom hashes for the Petya/Notpetya malware

Malicious PowerPoint Documents Abusing Mouse Over Actions

A new type of malicious MS Office document has appeared: a PowerPoint document that executes a PowerShell command by hovering over a link with the mouse cursor (this attack does not involve VBA macros). In this blogpost, we will show how to analyze such documents with free, open-source tools. As usual in attacks involving malicious … Continue reading Malicious PowerPoint Documents Abusing Mouse Over Actions

Using binsnitch.py to detect files touched by malware

Yesterday, we released binsnitch.py - a tool you can use to detect unwanted changes to the file sytem. The tool and documentation is available here: https://github.com/NVISO-BE/binsnitch. Binsnitch can be used to detect silent (unwanted) changes to files on your system. It will scan a given directory recursively for files and keep track of any changes it detects, based … Continue reading Using binsnitch.py to detect files touched by malware

Wcry ransomware – Additional analysis

Introduction Since May 12, a large number of organisations has fallen victim to the "wcry" (or "Wanacry") ransomware, which abuses the SMB exploits / vulnerabilities that were famously released in the Shadow Brokers data dump in April 2017. Our aim in this short blog post is not to repeat existing information, but communicate some additional … Continue reading Wcry ransomware – Additional analysis

Analysis of a CVE-2017-0199 Malicious RTF Document

There is a new exploit (CVE-2017-0199) going around for which a patch was released by Microsoft on 11/04/2017. In this post, we analyze an RTF document exploiting this vulnerability and provide a YARA rule for detection. rtfdump.py is a Python tool to analyze RTF documents. Running it on our sample produces a list with all "entities" … Continue reading Analysis of a CVE-2017-0199 Malicious RTF Document

Tracking threat actors through .LNK files

In the blog post .LNK downloader and bitsadmin.exe in malicious Office document we were asked the following question by Harlan Carvey: Did you parse the LNK file for things such as embedded MAC address, NetBIOS system name, any SID, and volume serial number? We did not do that at the time, however we see the value in … Continue reading Tracking threat actors through .LNK files