Smurf attacks are a type of protocol Distributed Denial of Service (DDoS) attack that exploit vulnerabilities in the Internet Control Message Protocol (ICMP). By abusing the broadcast functionality of a network, attackers flood the target system with amplified traffic, overwhelming its resources and causing service disruptions.
How Smurf Attacks Work
In a Smurf attack, the attacker sends a large number of ICMP Echo Request (ping) packets with a spoofed source IP address, set to the target’s IP. These packets are sent to a broadcast address, which causes all devices on the network to reply with ICMP Echo Replies to the spoofed source. The amplification effect occurs because a single ping request generates multiple replies, overwhelming the target system.
What Smurf Attacks Look Like in Logs
1. Large Volumes of ICMP Echo Replies
Logs show a sudden spike in ICMP Echo Replies directed at the target system.
Log Example (Firewall Logs):
[Nov 21 18:20:01] ICMP: Src=192.168.1.255 Dst=10.0.0.1 Type=0 Code=0
[Nov 21 18:20:02] ICMP: Src=192.168.1.255 Dst=10.0.0.1 Type=0 Code=0
[Nov 21 18:20:03] ICMP: Src=192.168.1.255 Dst=10.0.0.1 Type=0 Code=0
Signs:
- Multiple ICMP Echo Replies directed at the same target IP.
- Source address is a broadcast address (e.g.,
192.168.1.255).
2. High ICMP Traffic from Multiple Devices
The target experiences high volumes of ICMP traffic from various devices on the broadcast network.
Log Example (Firewall Logs):
[Nov 21 18:21:01] ICMP: Src=192.168.1.10 Dst=10.0.0.1 Type=0 Code=0
[Nov 21 18:21:02] ICMP: Src=192.168.1.11 Dst=10.0.0.1 Type=0 Code=0
[Nov 21 18:21:03] ICMP: Src=192.168.1.12 Dst=10.0.0.1 Type=0 Code=0
Signs:
- Multiple devices responding to the same spoofed request.
- A significant increase in ICMP traffic volume.