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Anthropic-Cybersecurity-Skills/skills/detecting-beaconing-patterns-with-zeek/SKILL.md
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---
name: detecting-beaconing-patterns-with-zeek
description: >
Performs statistical analysis of Zeek conn.log connection intervals to detect C2
beaconing patterns. Uses the ZAT library to load Zeek logs into Pandas DataFrames,
calculates inter-arrival time standard deviation, and flags periodic connections
with low jitter. Use when hunting for command-and-control callbacks in network data.
domain: cybersecurity
subdomain: security-operations
tags: [detecting, beaconing, patterns, with]
version: "1.0"
author: mahipal
license: MIT
---
# Detecting Beaconing Patterns with Zeek
## Instructions
Load Zeek conn.log data using ZAT (Zeek Analysis Tools), group connections by
source/destination pairs, and compute timing statistics to identify beaconing.
```python
from zat.log_to_dataframe import LogToDataFrame
import numpy as np
log_to_df = LogToDataFrame()
conn_df = log_to_df.create_dataframe('/path/to/conn.log')
# Group by src/dst pair and calculate inter-arrival time
for (src, dst), group in conn_df.groupby(['id.orig_h', 'id.resp_h']):
times = group['ts'].sort_values()
intervals = times.diff().dt.total_seconds().dropna()
if len(intervals) > 10:
std_dev = np.std(intervals)
mean_interval = np.mean(intervals)
# Low std_dev relative to mean = likely beaconing
```
Key analysis steps:
1. Parse Zeek conn.log into DataFrame with ZAT LogToDataFrame
2. Group connections by source IP and destination IP pairs
3. Calculate inter-arrival time intervals between consecutive connections
4. Compute standard deviation and coefficient of variation
5. Flag pairs with low coefficient of variation as potential beacons
## Examples
```python
from zat.log_to_dataframe import LogToDataFrame
log_to_df = LogToDataFrame()
df = log_to_df.create_dataframe('conn.log')
print(df[['id.orig_h', 'id.resp_h', 'ts', 'duration']].head())
```