Distributed-denial-of-service, or DDoS, attacks surged in the second quarter of 2015 compared with Q2 2014 and increased 7.13% from the first quarter of 2015, according to a survey of clients of Akamai Technologies Inc., a content delivery network and web security firm.

In its most recent “State of the Internet” report, the firm uncovered approximately 656 DDoS attacks in the second quarter of 2015. This finding comes after the combination of the Prolexic “State of the Internet” report with Akamai’s security report. The merger of these two studies allows Akamai, which bought Prolexic Technologies Inc. in late 2013, to more accurately report on DDoS attacks by tracking incidents on both the Akamai and Prolexic networks, the company says. The combined data is one reason attack numbers increased 132.4% year over year; 2015 is the first year to include combined data in the quarterly reports.

Of these attacks in the second quarter, 35.2% targeted clients in the gaming industry, 27.74% in the software and technology sector, 12.9% in Internet and telecom, 9.41% in media and entertainment, 8.19% in financial services, 2.6% in retail and consumer goods, 2.5% in education, 1.05% in the public sector and 0.41% in hotel and travel. That suggest that about 17 retail websites came under a denial-of-service attack. Akamai does not identify the clients targeted by these assaults.

A DDoS attack occurs when malefactors attempt to knock a site offline by sending an overwhelming volume of traffic to it. It’s distributed because the attack traffic comes from many computers, often thousands, which criminals control through software they surreptitiously load onto consumers’ PCs. Attackers often ask for money to call off the attack.

Here are the 10 countries that accounted for the most DDoS attack in the second quarter of 2015, with the percentage of attacks each accounted for among the top 10, and the comparable percentage for 2014:

• China, 37.01% of attack traffic among the top 10 countries, up from 12.3% in the second quarter of 2014.
• United States, 17.88%, down from 20.26%.
• United Kingdom, 10.21%, up from less than 4.44%.
• India, 7.43%, down from 8.26%.
• Spain, 6.03%, up from less than 4.44%.
• Korea, 4.53%, up from less than 4.44%.
• Russia, 4.45%, down from 4.87%.
• Germany, 4.29%, down from 10.3%.
• Australia, 4.18%, up from less than 4.44%.
• Taiwan, 4%, up from less than 4.44%.

(The 2015 percentages add up to 100%, but the 2014 percentages do not because different countries were in the top 10 list in Q2 2014.)

Instead of high-bandwidth, short duration threats that characterized attacks in Q2 2014, the trend since late 2014 and early this year reveals that malicious actors favor lower-bandwidth, higher-frequency and longer attacks, the report says. Gaming has remained the most targeted sector since Q2 2014, and attacks are often fueled by criminals seeking media attention, peer notoriety or looking to damage reputations or cause industry disruptions. Many of the largest console gaming networks were attacked in mid-June this year, which is when Akamai reported one of the three largest DDoS attacks ever in its network. The agency was unable to comment on the significance or details of this attack.