For the past two years we've been tinkering with a proof-of-concept decryptor for the Phobos family ransomware. It works, but is impractical to use for reasons we'll explain here. Consequently, we've been unable to use it to help a real-world victim so far. We've decided to publish our findings and tools, in hope that someone will find it useful, interesting or will continue our research. We will describe the vulnerability, and how we improved our decryptor computational complexity and performance to reach an almost practical implementation.

While working on our automatic configuration extractors, we came across a rather strange-looking Vidar sample. The decrypted strings included domain names of such organizations as the NATO Strategic Communications Centre of Excellence, Border Guard of Poland, Estonia and Latvia, and Ministry of the Interior of Lithuania. Automatically extracted strings from …

CloudEye (originally GuLoader) is a small malware downloader written in Visual Basic that's used in delivering all sorts of malicious payloads to victim machines. Its primary function is to download, decrypt and run an executable binary off a server (commonly a legitimate one like Google Drive or Microsoft OneDrive). At …

What’s up, Emotet? Emotet is one of the most widespread and havoc-wreaking malware families currently out there. Due to its modular structure, it’s able to easily evolve over time and gain new features without having to modify the core. Its first version dates back to 2014. Back then …

Yo dawg, I heard you like droppers so I put a dropper in your dropper On 2019-11-18 we received a report that some of Polish users have began receiving malspam imitating DHL: In this short article, we’ll take a look at the xls document that has been used as …

Smoke Loader (also known as Dofoil) is a relatively small, modular bot that is mainly used to drop various malware families. Even though it’s designed to drop other malware, it has some pretty hefty malware-like capabilities on its own. Despite being quite old, it’s still going strong, recently …

Backswap is a banker, which we first observed around March 2018. It’s a variant of old, well-known malware TinBa (which stands for “tiny banker”). As the name suggests, it’s main characteristic is small size (very often in the 10-50kB range). In the summary, we present reasoning for assuming …

Malicious scripts, distributed via spam e-mails, have been getting more complex for some time. Usually, if you got an e-mail with .js attachment, you could safely assume it’s just a simple dropper, which is limited to downloading and executing malware. Unfortunately, there is a growing number of campaigns these …

Analysis of a Polish BankBot Recently we have observed campaigns of a banking malware for Android system, which targets Polish users. The malware is a variant of the popular BankBot family, but differs from the main BankBot samples. Its victims were infected by installing a malicious application from Google Play …

Tofsee is a multi-purpose malware with wide array of capabilities – it can mine bitcoins, send emails, steal credentials, perform DDoS attacks, and more. All of this is possible because of its modular nature. We have already published about Tofsee/Gheg a few months ago – https://www.cert.pl/en/news …