A few weekends ago we participated in the Google CTF. While we didn't make it to the top 10, we did manage to solve quite a few challenges. This is my writeup of FlaggyBird, the only mobile challenge that was available. The challenge The challenge was an .apk that did not require network connectivity. Installing … Continue reading Solving Flaggy Bird (Google CTF 2019)
Firmware: the holy grail of most Internet of Things (IoT) security assessments! Sometimes, getting access to a device's firmware can be as easy as visiting the vendor's website. Other times, the only option is to dump it directly from the hardware, and this is where things get interesting. Some procedures used for dumping can expose … Continue reading Will they melt? Testing the resistance of flash memory chips
Since about a week, we are seeing an increase of SYLK files submitted to VirusTotal. A SYLK file (SYmbolic LinK) is a pure text file format used to store Excel spreadsheets with extension .slk. Although SYLK files can't contain VBA macros, they can still contain executable code, for example DDE commands or MS Excel 4.0 … Continue reading Malicious SYLK Files with MS Excel 4.0 Macros
In the previous blog post "Optimize Elasticsearch for log collection - Part 1: reduce the number of shards", we have seen one solution to recover a cluster suffering from the "too many shards syndrome" by merging indices that were too small. In this article, we'll see how we can rely on latest Elasticsearch feature to … Continue reading Optimizing Elasticsearch – Part 2: Index Lifecycle Management
Capture The Flag (CTF) competitions are an entertaining way to practice and/or improve your skills. NVISO staff regularly participates in CTF competitions, in particular when the competition focuses on IT security. We produced a video with step-by-step analysis of a CTF executable containing a buffer overflow. This executable is running on a server, and by … Continue reading Solving a CTF challenge: Exploiting a Buffer Overflow (video)
At first, it was just a simple team-building trip with less than ten participants. However, it became a tradition and year after year, more birds joined our nest and the trip grew bigger. After sharing stories and legends of previous years, both new joiners and veterans were waiting for the D-Day of this year’s famous … Continue reading The Birds Fly away!