Denial-of-service (DoS) attacks are usually exploited by hackers to interrupt regular network and website functioning, with motives of making money or for political reasons or simply to create a mess.  The websites or networks can be made unavailable through the Denial of Service (DoS) attack method which sends numerous requests for resources and traffic to the system. Researchers at CISPA Helmholtz-Center for Information Security discovered a new Denial-of-Service attack vector called “Application-layer Loop DoS Attacks.”  It targets UDP-based application protocols by pairing their servers to communicate indefinitely, affecting both legacy protocols like QOTD, Chargen, and Echo and contemporary ones like DNS, NTP, and TFTP.  This vulnerability puts an estimated 300,000 Internet hosts and networks at risk of denial-of-service conditions.

Source: GBHackers