# CIS Ubuntu 14.04 LTS - 3.2.4 Ensure suspicious packets are logged

> Verify that packets with un-routable source addresses are logged for investigation

- Skill: `cyberstrikeus/cis-ubuntu-14-04-lts-3-2-4-ensure-suspicious-packets-are-log` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-ubuntu-14-04-lts-3-2-4-ensure-suspicious-packets-are-log`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-ubuntu-14-04-lts-3-2-4-ensure-suspicious-packets-are-log/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/cyberstrikeus/cis-ubuntu-14-04-lts-3-2-4-ensure-suspicious-packets-are-log

---


# 3.2.4 Ensure suspicious packets are logged (Scored)

## Profile Applicability

- Level 1 - Server
- Level 1 - Workstation

## Description

When enabled, this feature logs packets with un-routable source addresses to the kernel log.

## Rationale

Enabling this feature and logging these packets allows an administrator to investigate the possibility that an attacker is sending spoofed packets to their system.

## Audit Procedure

Run the following commands and verify output matches:

```bash
sysctl net.ipv4.conf.all.log_martians
# Expected: net.ipv4.conf.all.log_martians = 1

sysctl net.ipv4.conf.default.log_martians
# Expected: net.ipv4.conf.default.log_martians = 1

grep "net\.ipv4\.conf\.all\.log_martians" /etc/sysctl.conf /etc/sysctl.d/*
# Expected: net.ipv4.conf.all.log_martians = 1

grep "net\.ipv4\.conf\.default\.log_martians" /etc/sysctl.conf /etc/sysctl.d/*
# Expected: net.ipv4.conf.default.log_martians = 1
```

## Expected Result

```
net.ipv4.conf.all.log_martians = 1
net.ipv4.conf.default.log_martians = 1
```

## Remediation

Set the following parameters in `/etc/sysctl.conf` or `/etc/sysctl.d/*` file:

```
net.ipv4.conf.all.log_martians = 1
net.ipv4.conf.default.log_martians = 1
```

Run the following commands to set the active kernel parameters:

```bash
sysctl -w net.ipv4.conf.all.log_martians=1
sysctl -w net.ipv4.conf.default.log_martians=1
sysctl -w net.ipv4.route.flush=1
```

## Default Value

Not specified. Note: It has been reported that due to Ubuntu bug #50093 this setting (and some others) can fail to apply properly on reboot requiring it to be manually re-applied. One method of accomplishing this is to add `sysctl -p` to run on reboot to your systems crontab.

## References

- CIS Controls: 6 - Maintenance, Monitoring, and Analysis of Audit Logs

## Profile

- Level 1 - Server
- Level 1 - Workstation