APT1, also known as the **Comment Crew**, is one of the most well-known Chinese state-sponsored hacking groups. They’re often associated with China’s People’s Liberation Army (PLA), specifically **Unit 61398**, based in Shanghai. These guys were essentially the poster children for Chinese cyber espionage in the early 2010s. ### The Basics: - **APT1** stands for **Advanced Persistent Threat 1**, a term coined by cybersecurity firm **Mandiant**. - The group earned the nickname **Comment Crew** because of their use of hidden commands in the comments of web pages to control malware—clever but sneaky. - They’ve been active since at least **2006**, though their origins may go back even further. ### What They Did: APT1 was prolific. They targeted **over 140 companies across 20 industries**, primarily in the **U.S.**, and **stole hundreds of terabytes** of data. Their victims included firms in aerospace, energy, manufacturing, and even media. Their primary goal was **economic espionage**—basically, helping Chinese companies gain a competitive edge by stealing proprietary information. Their operations often followed a clear pattern: 1. **Initial compromise** – often through phishing emails. 2. **Establishing backdoors** – using malware like **Gh0st RAT** or custom tools. 3. **Data exfiltration** – sometimes maintaining access for months or years. ### The Mandiant Report (2013): This was a huge deal. Mandiant (now part of FireEye) published a detailed report outing APT1 and linking them directly to the Chinese military. The report included: - IP addresses - Attack timelines - Details on malware and techniques - Even photos and personal info of some operatives allegedly involved This was one of the first times a private cybersecurity firm publicly **attributed a cyberespionage group to a nation-state** so directly and confidently. It caused a diplomatic stir—China denied everything, of course. ### Legacy: APT1 helped set the template for how modern cyber espionage is discussed and tracked. While their operations have supposedly been quiet since being exposed, it's likely they’ve just rebranded or merged with other PLA-linked operations (like **APT10** or **APT41**, which are also notorious Chinese hacking groups). Their exposure also kicked off a broader conversation about **state-sponsored hacking**, attribution, and the blurry lines between **cyber crime and cyber warfare**. APT1’s **toolkit** was extensive, and pretty sophisticated for its time. While not flashy like modern-day zero-day stockpiles, they had a reliable and well-organized arsenal of malware, backdoors, and infrastructure that let them stay inside networks **for months or even years** without detection. Here’s a breakdown of their greatest hits: --- ### 🐭 **Gh0st RAT** - This was their go-to backdoor. Think of it like their Swiss Army knife. - Gh0st RAT is a **Remote Access Trojan (RAT)** that lets attackers: - Capture keystrokes - Take screenshots - Control the mouse and keyboard - Turn on webcams/microphones - Exfiltrate files - It has been widely used by Chinese APT groups and was sometimes **customized by APT1** with tweaks to avoid detection or fit specific targets. --- ### 🔐 **Backdoors & Trojans** APT1 had a rotating cast of malware families. Some were off-the-shelf, others were homegrown or at least heavily modified. Here are a few worth mentioning: #### 1. **WEBC2** - A custom command and control (C2) system using HTTP/S, sometimes hidden in **webpage comment sections**—hence the “Comment Crew” nickname. - This allowed stealthy communication, as HTTP traffic looked "normal." #### 2. **MURX** - Another backdoor that let APT1 move laterally and maintain persistence. It was modular and could be tailored per mission. #### 3. **COOKIEBAG** - A credential-stealing tool used to harvest usernames, passwords, and session tokens—basically a way to go deeper once they got a foothold. --- ### 🛠️ **Tool Use Strategy** APT1 didn’t just spam malware—they were methodical. Once they got into a network: 1. **They'd dump credentials** using tools like **pwdump** or custom scripts. 2. **Move laterally** using stolen credentials, RDP, SMB, etc. 3. **Install backdoors** on multiple systems to maintain resilience. 4. **Use batch scripts and scheduled tasks** to automate persistence. 5. **Compress & exfiltrate data**—often using RAR or ZIP split archives to break large data into chunks for exfiltration. Sometimes they even **disabled antivirus** or deployed signed drivers to avoid detection. --- ### 🧠 Infrastructure & Obfuscation APT1 were pros at blending in: - Their C2 domains often mimicked legit businesses or services. - They used compromised U.S.-based systems as **hop points** to make attribution harder. - Many of their malware samples had **legit-looking file names** (like `svchost.exe`, `msupdate.exe`, etc.) to look innocuous to sysadmins. --- ### ⚠️ Operational Sloppiness (Sometimes) Despite being pretty advanced, they occasionally made rookie mistakes: - Reused IPs or domains across different campaigns - Didn't encrypt all traffic - Had debug strings in their malware - Left behind artifacts in English and Simplified Chinese These breadcrumbs were part of what allowed Mandiant to so confidently trace operations back to PLA Unit 61398. --- ### TL;DR APT1’s toolkit was like a **precision burglary kit**—backdoors, password stealers, file exfil tools—all backed by well-funded infrastructure and military-grade planning. They weren’t smashing windows to get in; they were copying keys, hiding in the walls, and stealing blueprints. If you're curious, I can pull apart one of their malware samples or explain how their C2 comms worked in detail—just say the word.