an single endpoint accessing windows administrative shares across a large number of endpoints is not common behavior. possible false positive scenarios include but are not limited to vulnerability scanners, administration systems and missconfigured systems.

Techniques

T1135

Sample rules

Windows Administrative Shares Accessed On Multiple Hosts

source: splunk
technicques:
- T1135

Description

The following analytic leverages Event IDs 5140 or 5145 to identify a source computer accessing windows administrative shares (C$, Admin$ and IPC$ ) across a large number remote endpoints. Specifically, the logic will trigger when a source endpoint accesses administrative shares across 30 or more target computers within a 5 minute timespan. This behavior could represent an adversary who is enumerating network shares across an Active Directory environment in the search for sensitive files, a common technique leveraged by red teamers and threat actors. As environments differ across organizations, security teams should customize the thresholds of this detection as needed.

Detection logic

 `wineventlog_security` EventCode=5140 OR EventCode=5145 (ShareName="\\\\*\\ADMIN$" OR ShareName="\\\\*\\IPC$" OR ShareName="\\\\*\\C$") 
| bucket span=5m _time 
| stats dc(Computer) AS unique_targets values(Computer) as host_targets values(ShareName) as shares by _time, IpAddress, SubjectUserName, EventCode 
| where unique_targets > 30 
| `windows_administrative_shares_accessed_on_multiple_hosts_filter`