What is Application-Level Denial of Service?
Application-Level Denial-of-Service (ALODS) is a common problem in many types of computer applications. The term “application-level” may refer to the type of software used, but it more often refers to the quality of the service provided to users. When a software application is used repeatedly and becomes bogged down by excessive resource utilization, a slow response from a computer server or other types of denial of service errors, the application’s overall performance will degrade. In the most severe cases, a service freeze may occur. Users may lose data or functionality when this happens.
Application-level DDoS is caused by several causes, including software code changes that have made it viable for attackers to create denial of service attacks. Some software applications, such as those used for medical transcription or gaming sites, are operated by terrorists to bring down computer networks. Other types of applications, such as those used for web browsing and emailing, are not vulnerable to this type of attack. Still, others may be. For an application-level attack to work, the attacker often must convince a victim’s system that a denial of service condition exists. It is possible to protect against these types of attacks by running continually updated software and running it in a manner that minimizes its vulnerability to attack.
In some cases, an application-level attack can be brought on simply by placing too much load on a server or network. For example, suppose a large amount of Internet traffic is generated by software that sends out excessive unsolicited emails. In that case, there is a high likelihood that the server will become overwhelmed and fail. The user may then connect to a different Internet server, which may serve their request correctly and block the connection. In this case, the user will receive a message that states, “Application-level blocking were applied.” In this case, the attack originated in the server where the application is installed and has not affected the other parts of the server or network.
In some other cases, applications used to monitor the Internet traffic going in and out of a given computer system might be susceptible to application-level denial of service attacks. For example, an application monitoring software package can detect if a particular application starts or stops and other actions occur while the program is in use. The monitoring software will report any unusual activity that it notices. These activities can include denial of access and denial of service attacks.
What is an application-level denial of service is often a result of server overload. If a server is busy, it will take longer to respond to requests. In addition, an overloaded server may send traffic in a format that is not expected, which is often visible through network monitoring tools. Traffic sent in the wrong form is much more likely to be ignored by network administrators and will not cause interference with other network systems.
Application-level attacks can be prevented by using appropriate server load balancing techniques. Servers should be selected according to the traffic they are intended to handle. There should be a good balance between their CPU activity and the number of resources they are consuming. If a server is overloaded, a denial of service attack can easily take place. This is why network administrators should monitor server load and disable unnecessary server processes if necessary.