iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
A Smurf attack is a denial-of-service attack that uses forged ICMP echo requests—the packets behind the ping command—to make multiple computers send replies to a victim at once. The computers on the broadcast network amplify the traffic, and that intermediary network can be disrupted along with the intended victim.
How a Smurf attack works
The classic attack involves three parties: an attacker, an intermediary network, and a victim. The attacker sends an ICMP echo request to the intermediary network’s IP broadcast address, but forges the packet’s source address so it appears to come from the victim. If the network forwards the broadcast and its hosts answer broadcast-directed echo requests, their replies go to the forged source address—the victim. CERT/CC describes the attack’s core components as forged ICMP echo requests and packets directed to IP broadcast addresses.
| # | Preview | Product | Price | |
|---|---|---|---|---|
| 1 |
|
Network Security, Firewalls, and VPNs | $66.62 | Buy on Amazon |
| 2 |
|
Network Security, Firewalls, and VPNs: . (Issa) | $60.09 | Buy on Amazon |
| 3 |
|
TP-Link ER605, Wired Gigabit VPN Router | $49.99 | Buy on Amazon |
| 4 |
|
Cybersecurity for Small Networks: A Guide for the Reasonably Paranoid | $33.22 | Buy on Amazon |
- Forge the source: The attacker sets the request’s source IP address to the victim’s address.
- Send to a broadcast address: The request targets an IP address that reaches multiple hosts on the intermediary network.
- Reflect the replies: Hosts that respond send echo replies to the victim. More than one intermediary network can be used, multiplying the traffic.
The intermediary is not just a conduit: the broadcast traffic and resulting replies can also degrade service there. A single request does not automatically create a large flood on every network. The effect depends on source-address spoofing being possible, broadcast forwarding, and hosts responding to broadcast-directed requests.
Quick wins for a faster PC:
Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Why the attack is called “Smurf”
The name comes from “smurf,” the name of an exploit program that CERT says was used to carry out the attack. The name does not refer to a particular network protocol; the classic technique relies on ICMP echo requests and IP broadcasts.
#1 Best Overall
History and what changed
CERT/CC issued its Smurf advisory on January 5, 1998, and last revised it on March 13, 2000. The advisory reported continuing attacks and advised administrators on preventing their networks from becoming either the source of attacks or intermediaries.
In 2006, the IETF described classic Smurf attacks as less serious than before, noting that routers generally dropped the relevant packets and end systems did not respond. That is a dated assessment, not a guarantee that every network today has those protections. RFC 4732 also discusses ingress filtering as a way to reduce source-address spoofing and amplification.
Rank #2
- Available with the Cloud Labs which provide a hands-on, immersive mock IT infrastructure enabling students to test their skills with realistic security scenarios
- New Chapter on detailing network topologies
- The Table of Contents has been fully restructured to offer a more logical sequencing of subject matter
- Introduces the basics of network security—exploring the details of firewall security and how VPNs operate
- Increased coverage on device implantation and configuration
The scale of a Smurf attack is not captured by a universal amplification ratio. The IETF’s 2013 RFC 6959 noted that 50,000 or more hosts might reside on a single subnet when explaining why large campus LANs could be especially susceptible. That is historical context, not a current measurement or a general multiplier for every attack. RFC 6959 does not establish a current, universal Smurf amplification factor.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
How IPv6 changes the picture
IPv6 does not use IP broadcast in the same way as IPv4, so the classic globally directed Smurf attack does not translate directly. A related local-link risk exists: a forged ICMPv6 echo request sent to the all-nodes link-local multicast address could prompt local hosts to reply to the spoofed source. The IETF says this risk is confined to the layer-2 network because IPv6 routers do not forward link-local destinations. It is not the same as a globally routed classic Smurf attack. RFC 9099 describes this IPv6 consideration.
Rank #3
- 【Five Gigabit Ports】1 Gigabit WAN Port plus 2 Gigabit WAN/LAN Ports plus 2 Gigabit LAN Port. Up to 3 WAN ports optimize bandwidth usage through one device.
- 【One USB WAN Port】Mobile broadband via 4G/3G modem is supported for WAN backup by connecting to the USB port. For complete list of compatible 4G/3G modems, please visit TP-Link website.
- 【Abundant Security Features】Advanced firewall policies, DoS defense, IP/MAC/URL filtering, speed test and more security functions protect your network and data.
- 【Highly Secure VPN】Supports up to 20× LAN-to-LAN IPsec, 16× OpenVPN, 16× L2TP, and 16× PPTP VPN connections.
- Security - SPI Firewall, VPN Pass through, FTP/H.323/PPTP/SIP/IPsec ALG, DoS Defence, Ping of Death and Local Management. Standards and Protocols IEEE 802.3, 802.3u, 802.3ab, IEEE 802.3x, IEEE 802.1q
What damage can it cause?
The victim may receive enough echo replies to degrade network performance or lose connectivity. The intermediary network can also suffer degraded performance or an outage. In a sufficiently large attack, providers serving either network may experience backbone degradation or peering saturation, extending the disruption beyond the immediate endpoints.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to reduce the risk
At the network boundary
- Configure routers and other boundary equipment to prevent forwarding of directed broadcasts.
- Filter packets with forged source addresses where feasible. Ingress filtering reduces the ability to send traffic with spoofed source IPs.
On hosts
- Configure systems not to answer ICMP echo requests sent to IP broadcast addresses, where the operating system and network design allow it.
- Do not rely on router settings alone: a compromised host inside a local network may still originate traffic there.
During an active flood
Contact the ISP if a victim is receiving a large stream of replies. Dropping the traffic at the victim’s router may not help if the upstream path is already congested; CERT notes that the ISP may need to block the traffic within its own network. The appropriate controls depend on the actual router, host operating system, and network design, so there is no single setting that applies to every deployment.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
