There're various security problems when we use internet. Here the list of few security problems over internet which could lead to misuse/loss of the data. These problems can be voided with few solutions.

1. Eves dropping: Reading others data illegally on the internet.
Solution:This problem is minimized by the encryption/decryption technique. We use a password called "key" to encrypt/decrypt a text file.

2. Tampering: Reading others data and also modifying it on the internet called tampering.
Solution:This can also be solved by encryption/decryption.

3. Impersonation: A person acting as another person on internet.
Solution:This can be solved by digital signature. A digital signature is a file that contain personal identification information. The information in these files is encrypted. People send digital signatures along with messages to avoid impersonation.

4. Virus: Virus is a harmful program that can damage data, software and hardware of a computer system. Virus generally comes through .exe (Executable file), .com (Command file), .doc (Document), audio, and video files. Virus can't carry through a plain text file.
Solution:Use plain text files or XML files to share the data and make sure that you're properly scanning the files while you receive them from others.

We used to have lot of security problems before the development of various technologies like Java, .NET etc. Java has been developed by considering all the above security problems over internet.