Rules: Base32 in DNS Query
By using base32, binary and text data can be encoded in a way that is fully compliant with DNS protocol specifications. Since common standard base32 uses 2-7 and the letters a-z, entropy must be measured to distinguish from normal text. The presence of long base32 encoding in a DNS query may indicate tunneling of information out of a network. Some security vendors and internet providers also use this technique to operate cloud infrastructure or transport information through firewalled environments.
| Detail | Value |
|---|---|
| Type | Match |
| Category | Exfiltration |
| Apply Risk to Entities | srcDevice_ip |
| Signal Name | Base32 in DNS Query |
| Summary Expression | Base32 in DNS Query from source host: {{srcDevice_ip}} |
| Score/Severity | Static: 2 |
| Enabled by Default | True |
| Prototype | False |
| Tags | _mitreAttackTactic:TA0011, _mitreAttackTechnique:T1132.001, _mitreAttackTechnique:T1132 |
- Amazon AWS - Route53
- Bro - Bro
- Cisco Systems - Umbrella
- Fortinet - Fortigate
- Infoblox - Network Identity Operating System
- Microsoft - Windows
- Netskope - WebTx
- Zscaler - Firewall
- Zscaler - Nanolog Streaming Service
| Origin | Field |
|---|---|
| Normalized Schema | dns_query |
| Normalized Schema | dns_queryDomain_alexaRank |
| Normalized Schema | dns_queryDomain_entropyFqdn |
| Normalized Schema | listMatches |
| Normalized Schema | srcDevice_ip |