Reverse Engineering on THALIUM

Symless: an IDA assistant for structure reconstruction

Tue, 13 Jan 2026 00:00:00 +0000

Symless is an IDA Pro plugin designed to assist with structure reconstruction and cross-reference placement. It comes in two flavors: an automatic pre-analysis that can reconstruct most of the structures used in a binary, and an interactive plugin that reconstructs a single structure from user selection.

We are now releasing a new architecture-agnostic version of Symless, and use this opportunity to describe its internal logic.

LLVM-powered deobfuscation of virtualized binaries

Fri, 22 Nov 2024 08:00:00 +0000

Virtualization is a powerful technique for code obfuscation, and reversing it can be challenging. In this post, we cover the work done during an internship on developing an automated devirtualization tool. We explore a simplified taint-based approach and discuss its limitations. For a more in-depth analysis, the full report is also made available.

Achieving Remote Code Execution in Steam: a journey into the Remote Play protocol

Mon, 04 Dec 2023 08:00:00 +0000

Remote Play Together, developed by Valve, allows sharing local multi-player games with friends over the network through streaming. The associated protocol is elaborate enough to shelter a valuable attack surface that has scarcely been ventured into in the past.

This post covers the reverse engineering of the protocol and client/server implementations inside Steam, before presenting a dedicated fuzzer that unveiled a few critical vulnerabilities.

ECW 2023: kaleidoscope (write-up)

Tue, 07 Nov 2023 12:00:00 +0100

kaleidoscope was a hard reverse engineering challenge created for the European Cyber Week CTF 2023 qualifiers, with a focus on Windows-specific mechanisms and VM-based obfuscation.

ECW 2021 - WriteUp

Mon, 25 Oct 2021 12:00:01 +0100

For the European Cyber Week CTF 2021 Thalium created some challenges in our core competencies: reverse and exploitation. This blog post presents some of the write-ups:

Chest (36 solve) - reverse
FSB as a service (3 solve) - exploitation
WYSIWYG (3 solve) - reverse
Pipe Dream (1 solve) - reverse
- the author posted his solution on his personal blog

Thalium’s challenges have been less resolved than others. They were not that difficult, but probably a bit more unexpected. A few additional challenges designed by Thalium are: