An active attack is a network exploit in which a hacker attempts to make changes to data on the target or data en route to the target.
Types of active attacks:
In a masquerade attack, the intruder pretends to be a particular user of a system to gain access or to gain greater privileges than they are authorized for. A masquerade may be attempted through the use of stolen login IDs and passwords, through finding security gaps in programs or through bypassing the authentication mechanism.
In a session replay attack, a hacker steals an authorized user’s log in information by stealing the session ID. The intruder gains access and the ability to do anything the authorized user can do on the website.
In a message modification attack, an intruder alters packet header addresses to direct a message to a different destination or modify the data on a target machine.
In a denial of service (DoS) attack, users are deprived of access to a network or web resource. This is generally accomplished by overwhelming the target with more traffic than it can handle.
In a distributed denial-of-service (DDoS) exploit, large numbers of compromised systems (sometimes called a botnet or zombie army) attack a single target.
Active attacks contrast with passive attacks, in which an unauthorized party monitors networks and sometimes scans for open ports and vulnerabilities. The purpose is to gain information about the target and no data is changed. However, passive attacks are often preparatory activities for active attacks.