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mukul975
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Complete skill folder anatomy across all cybersecurity skills: - scripts/agent.py: 80-150 line Python agents using real libraries (impacket, boto3, azure-mgmt-*, kubernetes, pefile, yara, scapy, shodan, stix2, etc.) - references/api-reference.md: real API documentation with method signatures - LICENSE: MIT license for all skill folders
1.6 KiB
1.6 KiB
API Reference: Performing DNS Tunneling Detection
scapy (DNS Packet Analysis)
from scapy.all import rdpcap, DNS, DNSQR, DNSRR, sniff
# Read from PCAP
packets = rdpcap("traffic.pcap")
for pkt in packets:
if pkt.haslayer(DNSQR):
qname = pkt[DNSQR].qname.decode()
qtype = pkt[DNSQR].qtype # 1=A, 16=TXT, 28=AAAA
# Live capture
def dns_callback(pkt):
if pkt.haslayer(DNSQR):
print(pkt[DNSQR].qname)
sniff(filter="udp port 53", prn=dns_callback, count=100)
Shannon Entropy Calculation
import math
from collections import Counter
def shannon_entropy(data):
counter = Counter(data)
length = len(data)
return -sum((c/length) * math.log2(c/length)
for c in counter.values())
# Normal domain: ~2.5-3.5 bits
# DNS tunnel: ~4.0-5.0 bits
DNS Tunneling Indicators
| Indicator | Threshold | Rationale |
|---|---|---|
| Subdomain entropy | > 3.8 | Encoded/encrypted data |
| Query length | > 50 chars | Payload in subdomain |
| TXT queries/domain | > 20/hour | Data channel |
| Unique subdomains | > 50/parent | Encoded sessions |
| Digit ratio | > 0.4 | Base64/hex encoding |
Common DNS Tunnel Tools
| Tool | Encoding | Record Types |
|---|---|---|
| iodine | Base128 | NULL, TXT, CNAME |
| dnscat2 | Hex/CNAME | TXT, MX, CNAME |
| dns2tcp | Base64 | TXT, KEY |
References
- scapy: https://scapy.readthedocs.io/en/latest/
- DNS tunneling detection: https://www.sans.org/white-papers/dns-tunneling/
- iodine: https://github.com/yarrick/iodine