a file server may experience high-demand loads that could cause this analytic to trigger.

Techniques

T1021.002

Sample rules

SMB Traffic Spike

source: splunk
technicques:
- T1021.002

Description

The following analytic detects spikes in Server Message Block (SMB) traffic connections, which are used for sharing files and resources between computers. It leverages network traffic logs to monitor connections on ports 139 and 445, and SMB application usage. By calculating the average and standard deviation of SMB connections over the past 70 minutes, it identifies sources exceeding two standard deviations from the average. This activity is significant as it may indicate potential SMB-based attacks, such as ransomware or data theft. If confirmed malicious, attackers could exfiltrate data or spread malware within the network.

Detection logic


| tstats `security_content_summariesonly` count FROM datamodel=Network_Traffic
  WHERE All_Traffic.dest_port=139
    OR
    All_Traffic.dest_port=445
    OR
    All_Traffic.app=smb
  BY _time span=1h, All_Traffic.src

| `drop_dm_object_name("All_Traffic")`

| eventstats max(_time) as maxtime

| stats count as num_data_samples max(eval(if(_time >= relative_time(maxtime, "-70m@m"), count, null))) as count avg(eval(if(_time<relative_time(maxtime, "-70m@m"), count, null))) as avg stdev(eval(if(_time<relative_time(maxtime, "-70m@m"), count, null))) as stdev
  BY src

| eval upperBound=(avg+stdev*2), isOutlier=if(count > upperBound AND num_data_samples >=50, 1, 0)

| where isOutlier=1

| table src count

| `smb_traffic_spike_filter`