There are different types of attacks in network security which can harm our data
Data Modification: After an attacker has examined your information, he can logically alter it. An attacker can modify the data in the knowledge of the sender or receiver. Even if confidentiality is not necessary for every communication, you would never want your messages to get change.
IP Address spoofing: networks, operating systems use this address of a computer to find a user. Sometimes an IP address of a user is falsely assumed.
After having a valid IP address of any user, the attacker can also alter, or delete your data.
Password-Based Attacks: your access to a computer and network resources are resolute by whom you are, i.e. your username and your password. When a hacker gets access to a user account, he can alter the data and has all the rights as the original account holder.