One-third of all /24 networks recently estimated to be active on the Internet have suffered at least one denial-of-service attack over the last two years.
That's the headline number from a two-year study conducted by the Center for Applied Internet Data Analysis (CAIDA), published last week.
CAIDA conducted the study to provide a “framework to enable a macroscopic characterisation of attacks, attack targets, and mitigation behaviours”.
To get that macroscopic view, the study's international group of six authors used two raw data sources: CAIDA's UCSD Network Telescope (explained here), and the AmpPot network of DDoS honeypots (here). Their two secondary data sources were OpenINTEL (an active DNS measurement project) and data gathered from DDoS prevention companies like Cloudflare and others.
Their data showed 2.2 million /24 networks (one third of the address space) experienced 20 million attacks during the study, either as direct DoS attacks or some kind of reflection attack, and 137,000 targets were hit by both kinds of attack.
Each day, three per cent of all registered Web domains are hosted on targeted IP addresses, the paper states, and over the two years, two-thirds of all Web sites were on IP addresses that were part of an attack.
It's no surprise that countries with the biggest presence on the Internet figure high as attack targets: America, China, France and Germany, for example. Russia is also a dangerous place.
The most popular protocols for a reflection attack are those that are most promiscuous in their responses: the Network Time Protocol (NTP) and the Domain Name System (DNS) make up more than 66 per cent of the data.
Third on the list is probably going to trigger nostalgia, though:
CHARGEN responses were still seen in more than 22 per cent of reflected attacks. ®
Bootnote: Direct denial-of-service attacks are straightforward: attackers try to hose Google.com by overloading an IP address like 220.127.116.11 with traffic.
In “reflected” attacks, an IP spoofs that IP address, issuing requests to a huge number of other hosts so that responses to 18.104.22.168 over load it. Responses collected by CAIDA for this study included “TCP SYN/ACK, TCP RST, ICMP Echo Reply, ICMP Destination Unreachable, ICMP Source Quench, ICMP Redirect, ICMP Time Exceeded, ICMP Parameter Problem, ICMP Timestamp Reply, ICMP Information Reply, or ICMP Address Mask Reply”.