Techniques
Sample rules
Excessive DNS Failures
- source: splunk
- technicques:
- T1071.004
- T1071
Description
The following analytic identifies excessive DNS query failures by counting DNS responses that do not indicate success, triggering when there are more than 50 occurrences. It leverages the Network_Resolution data model, focusing on DNS reply codes that signify errors. This activity is significant because a high number of DNS failures can indicate potential network misconfigurations, DNS poisoning attempts, or malware communication issues. If confirmed malicious, this activity could lead to disrupted network services, hindered communication, or data exfiltration attempts by attackers.
Detection logic
| tstats `security_content_summariesonly` count from datamodel=Network_Resolution where nodename=DNS "DNS.reply_code"!="No Error" "DNS.reply_code"!="NoError" DNS.reply_code!="unknown" NOT "DNS.query"="*.arpa" "DNS.query"="*.*" by "DNS.src" "DNS.query" "DNS.reply_code"
| `drop_dm_object_name("DNS")`
| lookup cim_corporate_web_domain_lookup domain as query OUTPUT domain
| where isnull(domain)
| lookup update=true alexa_lookup_by_str domain as query OUTPUT rank
| where isnull(rank)
| eventstats max(count) as mc by src reply_code
| eval mode_query=if(count=mc, query, null())
| stats sum(count) as count values(mode_query) as query values(mc) as max_query_count by src reply_code
| where count>50
| `get_asset(src)`
| `excessive_dns_failures_filter`