Denial of service is an attack that aims at preventing normal communication with a resource by disabling the resource itself, or by disabling an infrastructure device providing connectivity to it. The disabled resource could be in the form of customer data, website resources, or a specific service, to name a few. The most common form of DoS is to flood a victim with so much traffic that all available resources of the system are overwhelmed and unable to handle additional requests. The attacker floods the victim network with extremely large amounts of useless data or data requests, thereby overwhelming the net- work and rendering it useless or unavailable to legitimate users.
So what are the signs of a potential DoS attack? Well, there are a few that may indicate that a DoS attack may be in effect, such as:
- Unavailability of a resource
- Loss of access to a website
- Slow performance
- Increase in spam e-mails
Typical victims of DoS attacks range from government-owned resources to online vendors and others, and the intent of the attack is usually the deciding factor in terms of which target will be engaged. Consider a few simple examples to give you an idea of the impact of a successful DoS attack. From a corporate perspective, the focus is always on the bottom line. A successful DoS attack against a corporation’s web page or availability of back-end resources could easily result in a loss of millions of dollars in revenue depending on company size. Also, consider the negative impact to the brand name and company reputation. As you can see, the impact of a single DoS attack with specific directed intent can prove extremely damaging to the victim on many different levels.
Another theme that pervades DoS attacks, as well as other attack forms, is hackers who take action against a target based on “principle” or a sense of personal mission, which is known as hacktivism. Hacktivists are a particularly concerning threat because their focus is not necessarily on personal gain or recognition; their success is measured by how much their malicious actions benefit their cause. This thought process ties in nicely with DoS attacks in that the message being “sent” can be left up to interpretation or, more commonly, be claimed by a group or individual.
DoS attacks have also become extremely popular with cybercriminals and organized crime groups. These groups have organized themselves into complex hierarchies and structures designed to coordinate and magnify the effects of the attack. Additionally the groups use their organization to sometimes enact extortion schemes or to set up other moneymaking schemes.