# Cis Ubuntu1204 V110 7 2 5

> Enable Ignore Broadcast Requests

- Skill: `cyberstrikeus/cis-ubuntu1204-v110-7-2-5` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-ubuntu1204-v110-7-2-5`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-ubuntu1204-v110-7-2-5/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-ubuntu1204-v110-7-2-5

---


# 7.2.5 Enable Ignore Broadcast Requests (Scored)

## Profile Applicability

- Level 1

## Description

Setting `net.ipv4.icmp_echo_ignore_broadcasts` to 1 will cause the system to ignore all ICMP echo and timestamp requests to broadcast and multicast addresses.

## Rationale

Accepting ICMP echo and timestamp requests with broadcast or multicast destinations for your network could be used to trick your host into starting (or participating) in a Smurf attack. A Smurf attack relies on an attacker sending large amounts of ICMP broadcast messages with a spoofed source address. All hosts receiving this message and responding would send echo-reply messages back to the spoofed address, which is probably not routable. If many hosts respond to the packets, the amount of traffic on the network could be significantly multiplied.

## Audit Procedure

### Using Command Line

Perform the following to determine if all ICMP echo and timestamp requests to broadcast and multicast addresses will be ignored.

```bash
/sbin/sysctl net.ipv4.icmp_echo_ignore_broadcasts
```

## Expected Result

```
net.ipv4.icmp_echo_ignore_broadcasts = 1
```

## Remediation

### Using Command Line

Set the `net.ipv4.icmp_echo_ignore_broadcasts` parameter to 1 in `/etc/sysctl.conf`:

```bash
net.ipv4.icmp_echo_ignore_broadcasts=1
```

Modify active kernel parameters to match:

```bash
/sbin/sysctl -w net.ipv4.icmp_echo_ignore_broadcasts=1
/sbin/sysctl -w net.ipv4.route.flush=1
```

## Default Value

Broadcast ICMP requests are accepted by default.

## References

- CIS Ubuntu 12.04 LTS Server Benchmark v1.1.0

## Profile

Level 1 - Scored