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The cybercrime landscape continues to evolve, and in April 2025, a potent new player emerged on the scene: PupkinStealer. Designed to execute swift data theft attacks, this .NET-based infostealer exploits Telegram’s Bot API to smuggle sensitive user information out of compromised systems. Although its architecture avoids persistent installations and favors simplicity, the damage it causes can be extensive and immediate. With phishing campaigns and trojanized downloads serving as its primary delivery methods, PupkinStealer is proving itself to be a dangerous, evasive threat. Cybersecurity professionals are now racing to adapt their defenses against this increasingly common tactic of leveraging legitimate encrypted traffic for malicious purposes.
PupkinStealer: A Rapid-Fire Malware Built for Exfiltration
First flagged in April 2025, PupkinStealer (also appearing as PlutoniumLoader.exe) is a .NET executable weighing in at 6.21 MB. This malware doesn’t bother with complex persistence strategies — instead, it opts for a hit-and-run approach. It activates once executed by the user, gathers data almost instantly, and exits, leaving little trace behind.
The malware infiltrates Windows environments through phishing campaigns and rogue software downloads. Once activated, it initiates multiple asynchronous threads to carry out its data collection tasks at once. These include extracting saved credentials from Chromium-based browsers like Chrome, Edge, Opera, Brave, and Vivaldi, as well as harvesting Discord tokens and duplicating Telegram session files.
It
The stolen data is temporarily stored in a folder called “Grabbers” within the system’s temporary files path. It is then compressed into a ZIP archive using a naming format like [username]@ardent.zip, a tag that points to the Russian-speaking developer known as “Ardent.” Finally, all this data is exfiltrated via Telegram’s encrypted Bot API, sent to an attacker-controlled chat with hardcoded credentials and chat ID.
Unlike advanced malware, PupkinStealer
Security researchers have linked this malware to a Telegram bot handle, @botkanalchik_bot, and traced communications to api.telegram.org. By piggybacking on Telegram’s HTTPS traffic, the malware avoids triggering conventional detection systems. This method of data exfiltration reflects a growing trend among malware developers who use encrypted APIs to evade security tools and blend in with normal traffic.
Security experts recommend several defense strategies, including strict application allowlisting, monitoring for unusual access to credential storage, flagging communication with Telegram API endpoints, and scanning for suspicious ZIP files or Grabbers folders. If infection is suspected, immediate containment and credential revocation across platforms are critical.
What Undercode Say:
PupkinStealer signals a troubling evolution in the world of info-stealing malware — one where speed, simplicity, and abuse of trusted platforms like Telegram have become the defining traits of modern threats.
This malware is a clear example of tactical minimalism. It doesn’t waste time trying to maintain a long-term presence on the infected machine. Instead, it aims to harvest as much information as possible within a matter of seconds. This approach reflects a shift in attacker strategy — away from persistent backdoors and toward fast, volatile data theft that’s harder to catch in real time.
Using Telegram as an exfiltration channel is particularly clever. Telegram’s encrypted Bot API not only offers attackers a ready-made infrastructure but also allows the malware to blend in with legitimate HTTPS traffic. This creates significant challenges for defenders, who may find it hard to distinguish malicious activity from normal web usage without deeper inspection tools.
From a technical standpoint, PupkinStealer is not heavily armored. It lacks advanced anti-debugging or anti-analysis measures and doesn’t establish persistence. But that’s exactly what makes it dangerous. It’s light, fast, and performs a complete data sweep without the need for stealthy long-term mechanisms. That makes traditional endpoint protection tools, which often focus on persistent or continuously running threats, less effective.
Furthermore, its method of stealing authentication tokens and session files enables it to bypass multi-factor authentication in many cases. Once it hijacks a session from Telegram or Discord, the attacker gains full access without ever needing a password.
The use of the “@ardent” signature and Russian-language hints in the source code aligns with past malware campaigns emerging from Eastern Europe. While attribution remains speculative, it fits a pattern of nimble, modular infostealers being deployed for financial gain and identity theft.
PupkinStealer’s emergence emphasizes the need for behavioral monitoring rather than solely relying on signature-based antivirus tools. Organizations must also focus on educating users to avoid phishing lures and suspicious software, especially pirated applications that often act as infection vectors.
Network-level monitoring should also include flags for unusual outbound connections to Telegram APIs, especially those with the /bot/sendDocument endpoint pattern. Security teams should act quickly when suspicious ZIP files appear in temp directories or when apps crash without reason — both common indicators of this stealer’s activity.
This is a new breed of attack: rapid, volatile, and reliant on trusted platforms. As Telegram and similar services become more deeply integrated into users’ digital lives, they also become more attractive for misuse.
Fact Checker Results ✅
PupkinStealer is a verified malware sample identified by PicusSecurity, using Telegram Bot API for data exfiltration 🛡️
The “ardent” alias and Russian language clues align with known cybercrime behavior from Eastern European actors 🇷🇺
There is no indication of advanced AV evasion, but the malware’s speed and simplicity make it dangerous nonetheless ⚡
Prediction 🔮
As malware authors continue to explore encrypted APIs like Telegram’s for data theft, security vendors will likely develop new detection rules around encrypted messaging traffic. We expect similar lightweight infostealers to rise in popularity, possibly integrating more automation or AI-powered reconnaissance in future variants. If left unchecked, Telegram could become a go-to exfiltration tool for an entire generation of cybercriminal tools. Organizations must act now to adapt their defenses before this tactic becomes mainstream.
References:
Reported By: cyberpress.org
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