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Anthropic-Cybersecurity-Skills/skills/detecting-beaconing-patterns-with-zeek/SKILL.md
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mukul975 27c6414ca5 Add folder anatomy (scripts/agent.py + references/api-reference.md) for 648 cybersecurity skills
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2026-03-10 21:02:12 +01:00

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name, description
name description
detecting-beaconing-patterns-with-zeek 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.

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.

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

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())