26.2 Security Threat Categories
Security threats can be grouped into categories based on the nature of the threat and its impact on a system. Each category has its own characteristics that programmers need to be aware of, in order to address these security threats throughout the software lifecycle.
Denial-of-Service (DoS) Attacks
Denial-of-Service (DoS) attacks are a group of threats that are related to the way in which an application manages its resources—specifically, various attempts to exploit the lack of checks and restrictions around resource utilization. For example, a resource could be an open port, or a file, or memory allocation—in other words, something that an application needs for its operational requirements. The idea behind the DoS attack is to make requests to the application for its resources so that their availability for legitimate use is blocked. In DoS attack scenarios, the attacker is trying to exploit the lack of controls and restrictions that an application applies when it is allocating or accessing its resources.
The following scenarios are examples of DoS attacks:
- An attacker providing a very large file or document containing recursive references, causing the application to waste resources trying to parse such a document. This could cause the program to run out of memory, go into an infinite loop trying to handle the recursive execution, or simply slow down as it attempts to read a large document. In any case, this would impede this application’s ability to process legitimate data from other sources.
- An attacker opening a connection to a port through which the application performs network interactions. Once this connection is established, the attacker can start sending or receiving information in the slowest possible manner, causing the application to block for read or write operations to complete. The attacker can also spawn a large number of such connections, with the eventual goal of causing this application to run out of its capacity to handle simultaneous connections and denying service from legitimate users.
Countermeasures that can remedy DoS attacks include the following:
- Checking file sizes before starting parsing
- Detecting recursive references and stopping data processing if such recursions occur
- Discarding suspicious documents
- Detecting how many connections a given client has opened concurrently
- Detecting and terminating excessively slow uploads and downloads
- Dropping suspicious connections
- Limiting access to program logic to only authenticated and authorized code
Sometimes it might be the case that a legitimate user struggles with a network connection due to poor network quality. This means that slow connections must still be handled by the program. Consider using asynchronous I/O capabilities to handle these types of slow connections. Asynchronous I/O is supported in Java Enterprise Edition (EE)/Jakarta and MicroProfile servers.