MalwareUsed by 1 actor

MailSniper

MailSniper is a dual-use penetration-testing tool for searching email in Microsoft Exchange and Office 365 environments. It automates keyword-based mailbox searches to locate sensitive information, including passwords, internal intelligence, and network architecture details. These functions support remote email collection, credential discovery, and post-compromise reconnaissance. MailSniper also supports password spraying against Exchange and Office 365 to identify valid account credentials.

Although designed for legitimate security testing, MailSniper has been used in adversary operations. Leafminer obtained and used the tool to search Exchange server mailboxes for keywords. Its documented targets are enterprise email environments, including on-premises Exchange and cloud-hosted Office 365 services; it is not inherently a malware family.

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THREAT ACTORS

Groups observed using it

1 distinct threat actor attributed by public researchers. Open in Mallory to see the full evidence chain and overlapping campaigns.

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Leafminer

Leafminer has obtained and used tools such as LaZagne, Mimikatz, PsExec, and MailSniper.

via mitre attack websiteattack.mitre.org

MITRE ATT&CK

Techniques & procedures

5 distinct techniques documented for this family, organized by ATT&CK tactic.

Resource Development

1 technique

T1588.002ToolEvidence3

Adversaries may buy, steal, or download software tools that can be used during targeting. Tools can be open or closed source, free or commercial.

Credential Access

1 technique

T1110.003Password SprayingEvidence2

Adversaries may use a single or small list of commonly used passwords against many different accounts to attempt to acquire valid account credentials.

Discovery

1 technique

T1087Account DiscoveryEvidence1

Using the < OABUrl > path, you can get an Address List of all Exchange users.

Collection

2 techniques

T1114.001Local Email CollectionEvidence1

Mailsniper Invoke functions ... T1114.001 Data Exfiltration

T1114.002Remote Email CollectionEvidence6

Adversaries may also access externally facing Exchange services or Office 365 to access email using credentials or access tokens. Tools such as MailSniper can be used to automate searches for specific keywords.

ACTIVITY FEED

Recent activity

7 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

7 SOURCESView more in app

cyber security newsNews

Jan 6, 2026

Active Directory Attack Kill Chain Checklist & Tools List- 2026

MailSniper is a tool for searching Microsoft Exchange mailboxes for sensitive information, such as credentials or internal data, aiding in privilege escalation and data exfiltration.

mitre attack websiteNews

Oct 21, 2021

Brute Force: Password Spraying, Sub-technique T1110.003 - Enterprise | MITRE ATT&CK®

Offensive tool supporting password-spraying attacks against Exchange and Office 365 authentication.

mitre attack websiteNews

Oct 21, 2021

Obtain Capabilities: Tool, Sub-technique T1588.002 - Enterprise | MITRE ATT&CK®

Offensive tool acquired and used by Leafminer; its specific function is not described.

mitre attackNews

Jan 25, 2026

Brute Force: Password Spraying, Sub-technique T1110.003 - Enterprise | MITRE ATT&CK®

Tooling used to target Microsoft Exchange/Office 365, including password spraying capabilities.

+3 more in the timeline

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IOC matching

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Threat actor attribution1

Named campaigns wielding this family, with evidence pinned to each claim.

Exploited vulnerabilities

CVEs this family uses for access and lateral movement.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

MITRE ATT&CK mapping5

Every documented technique, ranked by evidence weight.

Researcher chatter

Reddit, Mastodon, and CTI community discussion around this family.

MailSniper