After the disappearance of almost 40 of the top 50 applications from Apple’s online application store, the reports of hacking and some suspicious online activities have been gaining a lot of ground. Some feel that hackers are responsible for these activities, while others are still not sure about the cause of these problems.

At least 40 of the applications developed by Thuat Nguyen are now among the top selling applications in the Books category. Most of these applications have claimed top spots, even though, very few people are aware of them and they have hardly been reviewed by anyone.

One of the developers, Alexandru Brie commented on his blog that the application developed by him, Self Help Classics was among the top 20 applications for the last 18 months, but it is now out of the top 50 list.

Other developers are also raising concerns that the Books category has been hacked by someone named mycompany/Thuat Nguyen.

These applications were removed by Apple from its U.S. Application Store on Monday. The Company did not give any statement regarding this matter.

On the other hand, the Next Web and Engadget, who first published these reports, feel that iTunes Store accounts have been hacked. People are also being advised to review their purchase history to ensure that their user accounts have not been hacked.

Tech experts are also advising people to change their passwords and try to include special characters and digits in their passwords.