Errors in computer programs are called "bugs". They may be benign and not affect the usefulness of the program, or have only subtle effects. But in some cases, they may cause the program or the entire system to "hang", becoming unresponsive to input such as mouse clicks or keystrokes, to completely fail, or to crash. Otherwise benign bugs may sometimes be harnessed for malicious intent by an unscrupulous user writing an exploit, code designed to take advantage of a bug and disrupt a computer's proper execution. Bugs are usually not the fault of the computer. Since computers merely execute the instructions they are given, bugs are nearly always the result of programmer error or an oversight made in the program's design.
Bugs are usually the fault of whom or what?
programmer error or an oversight made in the program's design

Denial of service attacks are designed to make a machine or network resource unavailable to its intended users. Attackers can deny service to individual victims, such as by deliberately entering a wrong password enough consecutive times to cause the victim account to be locked, or they may overload the capabilities of a machine or network and block all users at once. While a network attack from a single IP address can be blocked by adding a new firewall rule, many forms of Distributed denial of service (DDoS) attacks are possible, where the attack comes from a large number of points and defending is much more difficult. Such attacks can originate from the zombie computers of a botnet, but a range of other techniques are possible including reflection and amplification attacks, where innocent systems are fooled into sending traffic to the victim.
What does DDoS stand for?
Distributed denial of service

The Cadet Organizations Administration and Training Service (COATS) consists of officers and non-commissioned members who conduct training, safety, supervision and administration of nearly 60,000 cadets aged 12 to 18 years in the Canadian Cadet Movement. The majority of members in COATS are officers of the Cadet Instructors Cadre (CIC) branch of the CAF. Members of the Reserve Force Sub-Component COATS who are not employed part-time (Class A) or full-time (Class B) may be held on the "Cadet Instructor Supplementary Staff List" (CISS List) in anticipation of employment in the same manner as other reservists are held as members of the Supplementary Reserve.
Who is eligible to serve as a COATS trainer?
Reserve Force Sub-Component COATS