The number of DDoS attacks detected by Kaspersky jumped 18% year-on-year in the second quarter, according to the latest figures from the Russian AV vendor.

Although the number of detected attacks was down 44% from Q1, the vendor claimed that this seasonal change is normal as activity often dips in late spring and summer. However, the spike was even bigger when compared to the same period in 2017: an increase of 25%.

Application attacks, which the firm said are harder to defend against, increased by a third (32%) in Q2 2019 and now constitute nearly half (46%) of all detected attacks. The latter figure is up 9% from Q1 2019, and 15% from Q2 2018.

Crucially, the seasonal drop in attacks has barely touched targeting of the application layer, which fell just 4% from the previous quarter.

These attacks are difficult to detect and stop as they typically include legitimate requests, the firm said.

“Traditionally, troublemakers who conduct DDoS attacks for fun go on holiday during the summer and give up their activity until September. However, the statistics for this quarter show that professional attackers, who perform complex DDoS attacks, are working hard even over the summer months,” explained Alexey Kiselev, business development manager for the Kaspersky DDoS Protection team.

“This trend is rather worrying for businesses. Many are well protected against high volumes of junk traffic, but DDoS attacks on the application layer require them to identify illegitimate activity even if its volume is low. We therefore recommend that businesses ensure their DDoS protection solutions are ready to withstand these complex attacks.”

Kaspersky also recorded the longest DDoS attack since it started monitoring botnet activity in 2015. Analysis of commands received by bots from command and control (C&C) servers revealed one in Q2 2019 lasting 509 hours, which is nearly 21 days. The previous longest attack, observed in Q4 2018, lasted 329 hours.