DNS amplification attacks grew by 183 percent between January and August, according to a new report from Symantec.
Amplification and reflection attacks multiply the attack traffic and make it easier for attackers to take out large targets with small botnets, Symantec’s Candid Wueest explained.
“Distributed denial-of-service (DDoS) attacks are not a new concept, but they have proven to be effective,” he blogged. “In the last few years they have grown in intensity as well as in number, whereas the duration of an attack is often down to just a few hours. Such attacks are simple to conduct for the attackers, but they can be devastating for the targeted companies.”
In the report, Symantec states that the use of the Network Time Protocol (NTP) amplification method jumped substantially between January and July, but is now on the decline. Generic Internet Control Message Protocol (ICMP) flood attacks increased by 293 percent by the end of March, but dropped to 75 percent of the total amount of attacks observed in January by August.
“It is not uncommon to see fluctuations of different DDoS methods being used over time, as there are many factors at work that influence this,” according to the report. “Different attack groups have different preferences for their DDoS campaigns, for example ICMP flood attacks were one of the main methods used by the Darkness/Optima botnet. Some methods, particularly amplification attacks, may no longer work that well.”
Increasingly, Wueest noted, attackers are experimenting with protocols such as the Simple Network Management Protocol (SNMPv2) and the Simple Service Discovery Protocol (SSDP). Multiple methods are often used by attackers in order to make mitigation difficult, he added.
“Another trend seen in 2014 is the increase in Unix servers being compromised and their high bandwidth being used in DDoS attacks,” Wueest blogged. “PHP.Brobot and Backdoor.Piltabe are two examples of such threats, but the trend came to the forefront again when the ShellShock Bash vulnerability was exploited within hours of the bug’s discovery, allowing attackers to install DDoS scripts on a variety of servers. Various DDoS scripts and malicious ELF files were downloaded through the Bash vulnerability, creating a powerful DDoS botnet.”
DDoS-as-a-service is popular on underground hacking forums. These booter or stresser services are sometimes advertised as legitimate products for infrastructure stress tests, the report notes. Other providers are more blatant and do not hide their intentions.
“The prices range from US$5 to over $1,000, depending on the attack’s duration and size,” the report states. “While the sellers offer amplification attacks that could generate more than 100 Gbps of attack traffic, in reality the generated traffic seen is usually around 20-40 Gbps.”