Reconnaissance and discovery alerts

Typically, cyberattacks are launched against any accessible entity, such as a low-privileged user, and then quickly move laterally until the attacker gains access to valuable assets. Valuable assets can be sensitive accounts, domain administrators, or highly sensitive data. Microsoft Defender for Identity identifies these advanced threats at the source throughout the entire attack kill chain and classifies them into the following phases:

  1. Reconnaissance and discovery
  2. Persistence and privilege escalation alerts
  3. Credential access alerts
  4. Lateral movement alerts
  5. Other alerts

To learn more about how to understand the structure, and common components of all Defender for Identity security alerts, see Understanding security alerts. For information about True positive (TP), Benign true positive (B-TP), and False positive (FP), see security alert classifications.

The following security alerts help you identify and remediate Reconnaissance and discovery phase suspicious activities detected by Defender for Identity in your network.

Reconnaissance and discovery consist of techniques an adversary may use to gain knowledge about the system and internal network. These techniques help adversaries observe the environment and orient themselves before deciding how to act. They also allow adversaries to explore what they can control and what’s around their entry point to discover how it could benefit their current objective. Native operating system tools are often used toward this post-compromise information-gathering objective. In Microsoft Defender for Identity, these alerts usually involve internal account enumeration with different techniques.

Account enumeration reconnaissance (external ID 2003)

Previous name: Reconnaissance using account enumeration

Severity: Medium

Description:

In account enumeration reconnaissance, an attacker uses a dictionary with thousands of user names, or tools such as KrbGuess in an attempt to guess user names in the domain.

Kerberos: Attacker makes Kerberos requests using these names to try to find a valid username in the domain. When a guess successfully determines a username, the attacker gets the Preauthentication required instead of Security principal unknown Kerberos error.

NTLM: Attacker makes NTLM authentication requests using the dictionary of names to try to find a valid username in the domain. If a guess successfully determines a username, the attacker gets the WrongPassword (0xc000006a) instead of NoSuchUser (0xc0000064) NTLM error.

In this alert detection, Defender for Identity detects where the account enumeration attack came from, the total number of guess attempts, and how many attempts were matched. If there are too many unknown users, Defender for Identity detects it as a suspicious activity. The alert is based on authentication events from sensors running on domain controller and AD FS / AD CS servers.

Learning period:

None

MITRE:

Primary MITRE tactic Discovery (TA0007)
MITRE attack technique Account Discovery (T1087)
MITRE attack sub-technique Domain Account (T1087.002)

Suggested steps for prevention:

  1. Enforce Complex and long passwords in the organization. Complex and long passwords provide the necessary first level of security against brute-force attacks. Brute force attacks are typically the next step in the cyber-attack kill chain following enumeration.

Account Enumeration reconnaissance (LDAP) (external ID 2437) (Preview)

Severity: Medium

Description:

In account enumeration reconnaissance, an attacker uses a dictionary with thousands of user names, or tools such as Ldapnomnom in an attempt to guess user names in the domain.

LDAP: Attacker makes LDAP Ping requests (cLDAP) using these names to try to find a valid username in the domain. If a guess successfully determines a username, the attacker may receive a response indicating that the user exists in the domain.

In this alert detection, Defender for Identity detects where the account enumeration attack came from, the total number of guess attempts, and how many attempts were matched. If there are too many unknown users, Defender for Identity detects it as a suspicious activity. The alert is based on LDAP search activities from sensors running on domain controller servers.

Learning period:

None

MITRE:

Primary MITRE tactic Discovery (TA0007)
MITRE attack technique Account Discovery (T1087)
MITRE attack sub-technique Domain Account (T1087.002)

Network-mapping reconnaissance (DNS) (external ID 2007)

Previous name: Reconnaissance using DNS

Severity: Medium

Description:

Your DNS server contains a map of all the computers, IP addresses, and services in your network. This information is used by attackers to map your network structure and target interesting computers for later steps in their attack.

There are several query types in the DNS protocol. This Defender for Identity security alert detects suspicious requests, either requests using an AXFR (transfer) originating from non-DNS servers, or those using an excessive number of requests.

Learning period:

This alert has a learning period of eight days from the start of domain controller monitoring.

MITRE:

Primary MITRE tactic Discovery (TA0007)
MITRE attack technique Account Discovery (T1087), Network Service Scanning (T1046), Remote System Discovery (T1018)
MITRE attack sub-technique N/A

Suggested steps for prevention:

It's important to preventing future attacks using AXFR queries by securing your internal DNS server.

User and IP address reconnaissance (SMB) (external ID 2012)

Previous name: Reconnaissance using SMB Session Enumeration

Severity: Medium

Description:

Enumeration using Server Message Block (SMB) protocol enables attackers to get information about where users recently logged on. Once attackers have this information, they can move laterally in the network to get to a specific sensitive account.

In this detection, an alert is triggered when an SMB session enumeration is performed against a domain controller.

Learning period:

None

MITRE:

Primary MITRE tactic Discovery (TA0007)
MITRE attack technique Account Discovery (T1087), System Network Connections Discovery (T1049)
MITRE attack sub-technique Domain Account (T1087.002)

User and Group membership reconnaissance (SAMR) (external ID 2021)

Previous name: Reconnaissance using directory services queries

Severity: Medium

Description:

User and group membership reconnaissance are used by attackers to map the directory structure and target privileged accounts for later steps in their attack. The Security Account Manager Remote (SAM-R) protocol is one of the methods used to query the directory to perform this type of mapping. In this detection, no alerts are triggered in the first month after Defender for Identity is deployed (learning period). During the learning period, Defender for Identity profiles which SAM-R queries are made from which computers, both enumeration and individual queries of sensitive accounts.

Learning period:

Four weeks per domain controller starting from the first network activity of SAMR against the specific DC.

MITRE:

Primary MITRE tactic Discovery (TA0007)
MITRE attack technique Account Discovery (T1087), Permission Groups Discovery (T1069)
MITRE attack sub-technique Domain Account (T1087.002), Domain Group (T1069.002)

Suggested steps for prevention:

  1. Apply Network access and restrict clients allowed to make remote calls to SAM group policy.

Active Directory attributes reconnaissance (LDAP) (external ID 2210)

Severity: Medium

Description:

Active Directory LDAP reconnaissance is used by attackers to gain critical information about the domain environment. This information can help attackers map the domain structure, as well as identify privileged accounts for use in later steps in their attack kill chain. Lightweight Directory Access Protocol (LDAP) is one of the most popular methods used for both legitimate and malicious purposes to query Active Directory.

Learning period:

None

MITRE:

Primary MITRE tactic Discovery (TA0007)
MITRE attack technique Account Discovery (T1087), Indirect Command Execution (T1202), Permission Groups Discovery (T1069)
MITRE attack sub-technique Domain Account (T1087.002), Domain Groups (T1069.002)

Honeytoken was queried via SAM-R (external ID 2439)

Severity: Low

Description:

User reconnaissance is used by attackers to map the directory structure and target privileged accounts for later steps in their attack. The Security Account Manager Remote (SAM-R) protocol is one of the methods used to query the directory to perform this type of mapping. In this detection, Microsoft Defender for Identity will trigger this alert for any reconnaissance activities against a pre-configured honeytoken user

Learning period:

None

MITRE:

Primary MITRE tactic Discovery (TA0007)
MITRE attack technique Account Discovery (T1087)
MITRE attack sub-technique Domain Account (T1087.002)

Honeytoken was queried via LDAP (external ID 2429)

Severity: Low

Description:

User reconnaissance is used by attackers to map the directory structure and target privileged accounts for later steps in their attack. Lightweight Directory Access Protocol (LDAP) is one of the most popular methods used for both legitimate and malicious purposes to query Active Directory.

In this detection, Microsoft Defender for Identity will trigger this alert for any reconnaissance activities against a pre-configured honeytoken user.

Learning period:

None

MITRE:

Primary MITRE tactic Discovery (TA0007)
MITRE attack technique Account Discovery (T1087)
MITRE attack sub-technique Domain Account (T1087.002)

See also