DDoS Threat Report FHY 2021

Small bit-and-piece DDoS attacks boomed by 233% in the first half of 2021. As the pandemic carried on into 2021, hackers experimented with new attack patterns to avoid signature-based detection. More than 99% of all DDoS attacks were smaller than 10Gbps, as we had predicted in 2020. These small, nimble attacks can cripple communications service providers (CSPs) and Internet service providers (ISPs) if they leave detection to threshold or signature-based methods alone.

Key Observations:
  • Small but effective DDoS attacks prevalent in the first half of 2021: Rather than launching large bandwidth attacks against their targets, perpetrators now choose to employ attacks using high packet-rate loads of small-sized traffic from DDoS-for-hire services, with the aim of evading DDoS mitigation detection systems.
  • UDP attacks surge as DDoS tactics shift: UDP based attacks accounted for 43.69% of all attack cases in the first half of this year. Unlike in previous years where a large percentage of UDP attacks used DNS amplification to magnify the attack size against target networks, this half year saw only 26.08% of such attacks being employed. Instead, 3 different types of UDP-based attacks were identified.
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  • Bit-and-piece attacks continue to rise in number and severity: A 232.83% jump was recorded for bit-and-piece attacks compared with the latter half of 2020. Based on our findings, 39.94% of bit-and-piece attacks were significantly enhanced through the use of TCP ACK traffic as a new attack vector. During the first half of 2020, a total of 84 ASNs were impacted by bit-and-piece attacks. The total number of IP prefixes (Class C) attacked was 231.
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