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NTLM Relay Attack

Metadata

ID: 0xFF-0270-NTLM_Relay_Attack-Win

OS: WindowsEndpoint, WindowsServer

FP Rate: Low

ATT&CK Tags

Tactic Technique Subtechnique Technique Name
TA0006 - Credential Access T1557 001 Adversary-in-the-Middle - LLMNR/NBT-NS Poisoning and SMB Relay
TA0006 - Credential Access T1187 Forced Authentication

Utilized Data Sources

Log Provider Event ID Event Name ATT&CK Data Source ATT&CK Data Component
MDE ConnectionSuccess DeviceNetworkEvents Network Traffic Network Connection Creation
MDE LogonSuccess DeviceLogonEvents Logon Session Logon Session Creation

Technical description of the attack

​This query searches for successful NTLM network logins where the device name contained in the NTLM authentication message contains a device that is known to MDE, but the source IP address is different from the known source IP address for that specific device. This could indicate an attacker is relaying the NTLM authentication information. To remove false positives, this query also searches for an outgoing network connection from the initiator to the attacker.

Permission required to execute the technique

User

Detection description

NTLM relay attacks can be used by an attacker to authenticate to a system by relaying NTLM credentials that are taken from a different system. In an NTLM relay attack three machines are involved: the initiator, the attacker and the target. The initiator initiates an NTLM session to the attacker, the attacker then relays the NTLM authentication information to the target.

Considerations

None.

False Positives

None expected.

Suggested Response Actions

The query results can be used as a starting point for further investigations. The RemoteIP in the results contains the attacker's IP address.

Detection Blind Spots

The rule will only work if both the initiator and the target machines are enrolled in MDE.

References

Detection

Language: Kusto

Platform: M365 Security

Query:

let timeframe = 2*1d;
let DeviceIPs=(
    DeviceNetworkEvents
    | where ingestion_time() >= ago(timeframe)
    | where ActionType == "ConnectionAttempt" or ActionType == "ConnectionSuccess"
    | distinct DeviceName, LocalIP
    | extend DeviceName=tolower(split(DeviceName,".")[0])
);
// Find potential NTLM relay attack by looking for NTLM logins from devices that are known in MDE, but are from a source IP that does not match any known IP addresses for the device.
let PotentialNTLMRelayLogins=materialize (
    DeviceLogonEvents
    | where ingestion_time() >= ago(timeframe)
    | where ActionType == "LogonSuccess"
    | where LogonType == "Network"
    | where Protocol=="NTLM"
    | where isnotempty(RemoteDeviceName) and isnotempty(RemoteIP)
    | where RemoteIPType <> "Loopback"
    | extend RemoteDeviceName=tolower(RemoteDeviceName)
    | where RemoteDeviceName in ((DeviceIPs | project DeviceName)) // The remote device is known in MDE.
    | join kind=leftanti DeviceIPs on $left.RemoteIP == $right.LocalIP, $left.RemoteDeviceName == $right.DeviceName // The Remote IP does not match any known IP for the device.
    | project-reorder Timestamp, RemoteIP, RemoteDeviceName, AccountDomain, AccountName
);
// Filter the potential NTLM relay events by checking there was an outgoing SMB connection from the source device to the relay IP address.
DeviceNetworkEvents
| where ingestion_time() >= ago(timeframe)
| where RemotePort in (445, 80, 443, 9389)
| where RemoteIP in ((PotentialNTLMRelayLogins | project RemoteIP))
| extend ShortDeviceName=tolower(split(DeviceName,".")[0])
| where ShortDeviceName in ((PotentialNTLMRelayLogins | project RemoteDeviceName))
| lookup kind=inner PotentialNTLMRelayLogins on $left.ShortDeviceName == $right.RemoteDeviceName, $left.RemoteIP == $right.RemoteIP