LLMNR, or Link-Local Multicast Name Resolution, is a protocol used in modern versions of Windows operating systems for name resolution on local networks. It is similar to the mDNS (Multicast DNS) protocol used in macOS and Linux environments.
LLMNR allows for the resolution of domain names to IP addresses on a local network without the need for a DNS server. When a device on a network needs to resolve a hostname to an IP address, it sends out an LLMNR query to the local network asking if any other devices know the IP address associated with that hostname. If a device on the network knows the IP address, it responds to the query.
It's important to note that LLMNR operates within the local link or local subnet, and its queries and responses are sent using multicast addressing. It's generally used when DNS (Domain Name System) resolution is not available or when a DNS server is not configured.
LLMNR (Link-Local Multicast Name Resolution) uses User Datagram Protocol (UDP) on port 5355. This port is reserved for LLMNR communications. When a device on a local network needs to resolve a hostname to an IP address using LLMNR, it sends and receives queries and responses over UDP port 5355.
Port 137 is used by the NetBIOS Name Service (NBNS), also known as the NetBIOS over TCP/IP (NBT) Name Service. NetBIOS (Network Basic Input/Output System) is an early networking protocol used for communication between computers on a local network. Port 137 is specifically used for NetBIOS name resolution.
NetBIOS name resolution is used to translate NetBIOS names (computer names) to IP addresses. It's important to note that NetBIOS itself is not a secure protocol and has been largely deprecated in favor of more modern and secure networking protocols.
However, because LLMNR is a broadcast-based protocol and doesn't provide strong security features, it can potentially be used for malicious activities like DNS spoofing or man-in-the-middle attacks. Therefore, it's often recommended to disable LLMNR in secure network environments or use it cautiously in conjunction with other security measures.
LLMNR (Link-Local Multicast Name Resolution) has been exploited by some strains of ransomware to facilitate lateral movement and propagation within a network. Here's a typical scenario of how LLMNR can be used in a ransomware attack:
Initial Compromise: The ransomware gains initial access to a device within the network through phishing, exploitation of vulnerabilities, or other means.
Infiltration and Discovery: Once inside the network, the ransomware begins to move laterally to spread across the network. It may use tools or techniques to scan for vulnerable or poorly secured devices.
Exploiting LLMNR: The ransomware may utilize LLMNR to perform a type of attack called LLMNR poisoning or "LLMNR/NBT-NS spoofing." LLMNR poisoning involves responding to LLMNR requests on the local network with malicious information, effectively redirecting network traffic to the attacker-controlled system.
Redirecting Network Traffic: The ransomware sets up a rogue system that responds to LLMNR requests with its own IP address, impersonating a legitimate device on the network.
Lure and Exploit: Other devices on the network send LLMNR queries looking for a specific host. The malicious system, pretending to be the legitimate host, responds with its IP address.
Further Infiltration: Devices receiving the malicious response attempt to connect to the rogue system, believing it to be the legitimate host. The ransomware gains access to these devices, spreading further within the network.
Encrypting Data: The ransomware proceeds to encrypt files and data on the newly compromised devices, rendering them inaccessible and demanding a ransom for decryption.
Exploiting LLMNR in this manner enables the ransomware to rapidly propagate and infect multiple devices within the network, increasing the impact of the attack and potentially causing severe disruptions and data loss.
Title: Ransomware Attack Exploiting LLMNR
Step 1: Initial Compromise
The attacker gains initial access to a corporate network by exploiting a vulnerable remote desktop service.
Step 2: Infiltration and Reconnaissance
The attacker begins reconnaissance within the compromised system, identifying potential targets and weaknesses.
Step 3: Identifying LLMNR Vulnerability
The attacker scans the network and identifies devices with LLMNR enabled.
Step 4: Setting Up Rogue System
The attacker sets up a rogue system within the network, which will respond to LLMNR queries.
Step 5: Exploiting LLMNR
A legitimate user on a different device sends an LLMNR query for a specific host name.
Step 6: Traffic Redirection
The rogue system responds to the LLMNR query, impersonating the legitimate host.
Step 7: Establishing Connection with Rogue System
The legitimate device establishes a connection with the rogue system, believing it to be the real host.
Step 8: Lateral Movement and Propagation
The attacker exploits the compromised device to move laterally within the network, infecting other devices with ransomware.
Step 9: Deploying Ransomware
The attacker deploys ransomware on the compromised devices, encrypting files and data.
Step 10: Ransom Demand
The attacker sends a ransom demand to the organization, demanding payment in cryptocurrency for decryption keys.
Step 11: Encryption and Data Loss
The ransomware encrypts critical files and data, causing data loss and disrupting normal operations.
Again, please note that this is a simplified, hypothetical scenario to illustrate how an attacker might potentially exploit LLMNR in a ransomware attack. In real-world situations, such attacks can be much more complex and involve multiple techniques and tactics. It's crucial for organizations to have robust cybersecurity measures in place to prevent and respond to such threats.
Conclusion
To mitigate the risk associated with LLMNR-based attacks, it's essential to follow best security practices, including disabling unnecessary network protocols like LLMNR and implementing network segmentation, robust access controls, regular security updates, and educating users about phishing and other security threats.