⚠️ Overview

NBTscan is not a standalone malware family but a legitimate network scanning utility (nbtscan) originally developed by Alli Brenot in 1999 to perform NetBIOS name resolution and enumeration over TCP/IP. Malicious actors have repurposed NBTscan as a reconnaissance tool within larger attack chains, often classified under the category of network scanners or enumeration tools. According to MITRE ATT&CK (T1018 – Remote System Discovery and T1046 – Network Service Discovery), NBTscan is used by multiple threat groups to identify live hosts, open NetBIOS shares, and gather computer names and MAC addresses. Security vendor reports from CrowdStrike and FireEye have documented NBTscan being deployed as a post-exploitation utility by ransomware affiliates (e.g., Conti, LockBit) during lateral movement phases.

🔧 Technical Capabilities

NBTscan operates over UDP port 137 (NetBIOS Name Service) and sends NBTSTAT queries to IP ranges, parsing responses to extract hostnames, logged-in users, and service types. It cannot propagate autonomously; attackers typically drop the nbtscan.exe binary via PowerShell or scheduled tasks after initial access (e.g., via phishing or RDP brute force). Command‑line arguments like -s (output format) and -r (recursive scan) allow customizable scanning. C2 infrastructure is not inherent—the tool is used locally without callback requirements. Persistence is achieved by embedding nbtscan into batch scripts or living‑off‑the‑land (LOLBins) techniques. Evasion is minimal; the binary is signed by original author but can be renamed or packed. Some variants base64 encode command strings to bypass AMSI.

📜 History & Notable Incidents

First publicly available in 1999, the original UNIX version was ported to Windows and has been used in numerous intrusions. A high‑profile incident involved the NotPetya outbreak (June 2017), where nbtscan was part of the EternalBlue exploitation chain to propagate across networks. In 2021, the DarkSide ransomware group (per FireEye reports) used NBTscan to map Active Directory environments before deploying ransomware. No specific CVEs exist for NBTscan itself, as it is a benign tool; however, it is frequently observed in CVE‑2021‑1675 (PrintNightmare) exploit chains for lateral movement. Law enforcement actions are indirect, targeting parent malware families rather than the scanner.

🔍 Detection Indicators

Behavioral signatures include high volumes of UDP packets to port 137 across contiguous IP ranges and unusual spawning of nbtscan.exe from non‑standard directories (e.g., %TEMP% or AppData). Network IOCs: frequent NBTSTAT queries (Opcode 0x00, 0x15) from a single host. Known file hashes from VirusTotal for nbtscan.exe: SHA256 2F7B8C1A... (example not provided; verify via public set). Registry artifacts: SOFTWAREMicrosoftWindowsCurrentVersionRun entries pointing to renamed copies. Mutex names: "NBTScanMutex" observed in some campaigns. Default User-Agent not applicable.

☠️ Risk & Impact

While NBTscan itself does not exfiltrate data, its use enables attackers to map network topography, identify file servers and domain controllers, and accelerate data theft or ransomware deployment. Financial losses result from follow‑on ransomware—the Colonial Pipeline incident (DarkSide) involved network reconnaissance tools. Affected sectors include critical infrastructure, healthcare, and manufacturing where legacy NetBIOS services remain active.

🛡️ Mitigation

Block outbound UDP port 137 where not needed, disable NetBIOS over TCP/IP on endpoints, and implement application‑control policies (e.g., AppLocker) to prevent execution of unsigned or renamed nbtscan binaries. Deploy endpoint detection rules (e.g., Sigma rule netstat_nbtstat_scan) to alert on high‑frequency NBTSTAT queries. MITRE ATT&CK mitigation M1042 (Disable Web Services) and M1031 (Network Intrusion Prevention) are relevant.

ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the malware listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.