NTLM Relay Attack

Group by: RemoteDeviceName, RemoteIP, ShortDeviceName
Author: FalconForce
Source: github.com/FalconForceTeam/FalconFriday

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.

Known false positives

None expected.

MITRE ATT&CK coverage

Tactic	Techniques
Credential Access	`T1187` Forced Authentication `T1557.001` Adversary-in-the-Middle: Name Resolution Poisoning and SMB Relay

References

https://github.com/Cyb3r-Monk/Threat-Hunting-and-Detection/blob/main/Credential%20Access/Potentially%20Relayed%20NTLM%20Authentication%20-%20MDE.md

Telemetry coverage

Platform	Record / event type
Microsoft Defender for Endpoint	`DeviceLogonEvents` action `LogonSuccess`: Logon succeeded
Microsoft Defender for Endpoint	`DeviceNetworkEvents` action `ConnectionAttempt`: Connection attempted
Microsoft Defender for Endpoint	`DeviceNetworkEvents` action `ConnectionSuccess`: Connection succeeded
Microsoft Defender for Endpoint	`DeviceNetworkEvents` action `any`: Network activity

Rule body

let timeframe = 2*1d;
// Extract a list of known local IPs per device. Note that the DeviceNetworkEvents table is used for this, since this is faster than the
// DeviceNetworkInfo table where IP addresses are stored inside a JSON structure that requires additional parsing.
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, 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
| extend HostName=tostring(split(DeviceName,".")[0]),DnsDomain=iif(DeviceName contains ".", substring(DeviceName, indexof(DeviceName, ".") + 1, strlen(DeviceName)),"")
// Begin environment-specific filter.
// End environment-specific filter.

Stages and Predicates

Parameters

let timeframe = 2*1d;

Let binding: `DeviceIPs` used in Stage 1

let DeviceIPs = (
    DeviceNetworkEvents
    | where ingestion_time() >= ago(timeframe)
    | where ActionType == "ConnectionAttempt" or ActionType == "ConnectionSuccess"
    | distinct DeviceName, LocalIP
    | extend DeviceName=tolower(split(DeviceName,".")[0])
);

Let binding: `PotentialNTLMRelayLogins` used in Stages 2, 9

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))
    | join kind=leftanti DeviceIPs on $left.RemoteIP == $right.LocalIP, $left.RemoteDeviceName == $right.DeviceName
    | project-reorder Timestamp, RemoteIP, RemoteDeviceName, AccountDomain, AccountName
);

Stage 1: `source`

let DeviceIPs

Stage 2: `source`

let PotentialNTLMRelayLogins

Stage 3: `source`

DeviceNetworkEvents

Stage 4: `where`

where ...

Stage 5: `where`

where RemotePort in~ (445, 80, 9389)

Stage 6: `where`

where /* macro: (RemoteIP in <NestedQuery>) */

Stage 7: `extend`

extend ShortDeviceName

Stage 8: `where`

where /* macro: (ShortDeviceName in <NestedQuery>) */

Stage 9: `kusto:lookup`

lookup kind=inner (PotentialNTLMRelayLogins) on ShortDeviceName, RemoteDeviceName, RemoteIP, RemoteIP

Stage 10: `extend`

extend DnsDomain, HostName

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`ActionType`	eq	`ConnectionAttempt` `ConnectionSuccess` `LogonSuccess`	`field:"ActionType" kind:eq`
`LogonType`	eq	`Network`	`field:"LogonType" kind:eq value:"Network"`
`Protocol`	eq	`NTLM`	`field:"Protocol" kind:eq value:"NTLM"`
`RemoteDeviceName`	is_not_null	(no value, null check)	`field:"RemoteDeviceName" kind:is_not_null`
`RemoteIP`	is_not_null	(no value, null check)	`field:"DestinationIp" kind:is_not_null`
`RemoteIPType`	ne	`Loopback`	`field:"RemoteIPType" kind:ne value:"Loopback"`
`RemotePort`	in	`445` `80` `9389`	`field:"DestinationPort" kind:in`

Output fields

These fields are emitted when the rule matches.

Field	Source
`ShortDeviceName`	`extend`
`DnsDomain`	`extend`
`HostName`	`extend`

NTLM Relay Attack

Known false positives

MITRE ATT&CK coverage

References

Telemetry coverage

Rule body

Stages and Predicates

Parameters

Let binding: DeviceIPs used in Stage 1

Let binding: PotentialNTLMRelayLogins used in Stages 2, 9

Stage 1: source

Stage 2: source

Stage 3: source

Stage 4: where

Stage 5: where

Stage 6: where

Stage 7: extend

Stage 8: where

Stage 9: kusto:lookup

Stage 10: extend