Malware

PostNapTea

Also known as: SIGNBT

PostNapTea aka SIGNBT is an HTTP(S) RAT that is written as a complex object-oriented project. In 2022-2023, it was deployed against targets like a newspaper organization, agriculture-related entity or a software vendor. The initial access was usually achieved by exploiting vulnerabilities in widely-used software in South Korea. It collects various information about the victim’s computer, such as computer name, product name, OS details, system uptime, CPU information, system locale, time zone, network status, and malware configuration. PostNapTea uses AES for encryption and decryption ot network traffic. There is a constant prefix SIGNBT occuring in its HTTP POST requests. The prefix is concatenated with 2 characters that identify the communication stage: • LG: logging into the C&C server • KE: acknowledging the succesful login to the C&C • FI: sending the status of a failed operation • SR: sending the status of a successful operation • GC: getting the next command There are five classes that represent command groups: • CCButton: for file manipulation and screen capturing • CCBitmap: for network commands, implementing functionality of Windows commands often abused by attackers, like sc, reg, arp, net, ver, wmic, ping, whoami, netstat, tracert, lookup, ipconfig, systeminfo, and netsh advfirewall. • CCComboBox: for file system management • CCList: for process management • CCBrush: for control of the malware itself It stores its configuration in JSON format. It resolves the Windows APIs it requires during runtime, via the Fowler–Noll–Vo (FNV) hash function. Its internal name in the version-information resource is usually ppcsnap.dll or pconsnap.dll, which loosely inspired its code name.

Indicators of Compromise 6

Domain jshosting[.]me Filename SearchHost.exe Filename inet.tmp Filename net.tmp Filename task.vbs IP 176[.]65[.]128[.]26

MITRE ATT&CK TTPs 11

T1001.001
Junk Data
Command And Control
 T1021.001
Remote Desktop Protocol
Lateral Movement
 T1055
Process Injection
Defense Evasion
 T1059.001
PowerShell
Execution
 T1070.004
File Deletion
Defense Evasion
 T1071.001
Web Protocols
Command And Control
 T1078
Valid Accounts
Defense Evasion
 T1085
T1085
 T1098
Account Manipulation
Persistence
 T1189
Drive-by Compromise
Initial Access
 T1203
Exploitation for Client Execution
Execution

Source Articles

Hackers Exploit AnySign4PC via Hacked Korean Sites to Install Backdoors Without Prompts
A state-sponsored threat actor has conducted a campaign exploiting a zero-day buffer overflow vulnerability in AnySign4PC, a South Korean financial-security software, through compromised legitimate websites used as watering holes. The attack allows remote code execution without user interaction by leveraging malicious WebSocket communication and DLL side-loading, leading to the deployment of SIGNBT or COPPERHEDGE backdoors. These backdoors enable remote command execution, file theft, reconnaissance, and lateral movement using tools like Mimikatz and RDP. The campaign overlaps technically with Gunra ransomware operations in infrastructure and artifacts, though no formal attribution to a specific group like Lazarus is made in the joint advisory.
hacker-news ·5h ago