Adversaries may sniff network traffic to capture information about an environment, including authentication material passed over the network. Network sniffing refers to using the network interface on a system to monitor or capture information sent over a wired or wireless connection. An adversary may place a network interface into promiscuous mode to passively access data in transit over the network, or use span ports to capture a larger amount of data.
Data captured via this technique may include user credentials, especially those sent over an insecure, unencrypted protocol. Techniques for name service resolution poisoning, such as LLMNR/NBT-NS Poisoning and SMB Relay, can also be used to capture credentials to websites, proxies, and internal systems by redirecting traffic to an adversary.
Network sniffing may also reveal configuration details, such as running services, version numbers, and other network characteristics (e.g. IP addresses, hostnames, VLAN IDs) necessary for subsequent Lateral Movement and/or Defense Evasion activities.
In cloud-based environments, adversaries may still be able to use traffic mirroring services to sniff network traffic from virtual machines. For example, AWS Traffic Mirroring, GCP Packet Mirroring, and Azure vTap allow users to define specified instances to collect traffic from and specified targets to send collected traffic to.[1] [2] [3] Often, much of this traffic will be in cleartext due to the use of TLS termination at the load balancer level to reduce the strain of encrypting and decrypting traffic.[4] [5] The adversary can then use exfiltration techniques such as Transfer Data to Cloud Account in order to access the sniffed traffic. [4]
| ID | Name | Description |
|---|---|---|
| G0007 | APT28 |
APT28 deployed the open source tool Responder to conduct NetBIOS Name Service poisoning, which captured usernames and hashed passwords that allowed access to legitimate credentials.[6][7] APT28 close-access teams have used Wi-Fi pineapples to intercept Wi-Fi signals and user credentials.[8] |
| G0064 | APT33 |
APT33 has used SniffPass to collect credentials by sniffing network traffic.[9] |
| G0105 | DarkVishnya |
DarkVishnya used network sniffing to obtain login data. [10] |
| S0367 | Emotet |
Emotet has been observed to hook network APIs to monitor network traffic. [11] |
| S0363 | Empire |
Empire can be used to conduct packet captures on target hosts.[12] |
| S0661 | FoggyWeb |
FoggyWeb can configure custom listeners to passively monitor all incoming HTTP GET and POST requests sent to the AD FS server from the intranet/internet and intercept HTTP requests that match the custom URI patterns defined by the actor.[13] |
| S0357 | Impacket |
Impacket can be used to sniff network traffic via an interface or raw socket.[14] |
| G0094 | Kimsuky |
Kimsuky has used the Nirsoft SniffPass network sniffer to obtain passwords sent over non-secure protocols.[15][16] |
| S0443 | MESSAGETAP |
MESSAGETAP uses the libpcap library to listen to all traffic and parses network protocols starting with Ethernet and IP layers. It continues parsing protocol layers including SCTP, SCCP, and TCAP and finally extracts SMS message data and routing metadata. [17] |
| S0590 | NBTscan | |
| S0587 | Penquin |
Penquin can sniff network traffic to look for packets matching specific conditions.[20][21] |
| S0378 | PoshC2 |
PoshC2 contains a module for taking packet captures on compromised hosts.[22] |
| S0019 | Regin |
Regin appears to have functionality to sniff for credentials passed over HTTP, SMTP, and SMB.[23] |
| S0174 | Responder |
Responder captures hashes and credentials that are sent to the system after the name services have been poisoned.[24] |
| G0034 | Sandworm Team |
Sandworm Team has used intercepter-NG to sniff passwords in network traffic.[25] |
| ID | Mitigation | Description |
|---|---|---|
| M1041 | Encrypt Sensitive Information |
Ensure that all wired and/or wireless traffic is encrypted appropriately. Use best practices for authentication protocols, such as Kerberos, and ensure web traffic that may contain credentials is protected by SSL/TLS. |
| M1032 | Multi-factor Authentication |
Use multi-factor authentication wherever possible. |
| M1018 | User Account Management |
In cloud environments, ensure that users are not granted permissions to create or modify traffic mirrors unless this is explicitly required. |
| ID | Data Source | Data Component |
|---|---|---|
| DS0017 | Command | Command Execution |
| DS0009 | Process | Process Creation |
Detecting the events leading up to sniffing network traffic may be the best method of detection. From the host level, an adversary would likely need to perform a Adversary-in-the-Middle attack against other devices on a wired network in order to capture traffic that was not to or from the current compromised system. This change in the flow of information is detectable at the enclave network level. Monitor for ARP spoofing and gratuitous ARP broadcasts. Detecting compromised network devices is a bit more challenging. Auditing administrator logins, configuration changes, and device images is required to detect malicious changes.
In cloud-based environments, monitor for the creation of new traffic mirrors or modification of existing traffic mirrors.