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Network Share Discovery Via Dir Command

The following analytic detects access to Windows administrative SMB shares (Admin$, IPC$, C$) using the 'dir' command. It leverages Windows Security Event Logs with EventCode 5140 to identify this activity. This behavior is significant as it is commonly used by tools like PsExec/PaExec for staging binaries before creating and starting services on remote endpoints, a technique often employed by adversaries for lateral movement and remote code execution. If confirmed malicious, this activity could allow attackers to propagate malware, such as IcedID, across the network, leading to widespread infection and potential data breaches.

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Detection Logic

`wineventlog_security`
EventCode=5140
ShareName IN (
    "\\\\*\\Admin$",
    "\\\\*\\C$",
    "\\\\*\\IPC$"
)


```
We select only read-related operations:
    0x1 = ReadData (or ListDirectory)
```
| eval AccessMask_ = tonumber(AccessMask, 16)
| where (bit_and(AccessMask_, 1) != 0)
| stats min(_time) as firstTime
        max(_time) as lastTime
        count

by ShareName IpAddress ObjectType SubjectUserName
   SubjectDomainName IpPort AccessMask Computer
| rename Computer as dest
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `network_share_discovery_via_dir_command_filter`

False Positives

⚠ System Administrators may use tools like "net.exe", "net1.exe", or "dir" for troubleshooting or administrations tasks. However, this will typically come only from certain users and certain systems that can be added to an allow list.

Field Validations

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