strange messages in log file @^@^@^@^@^@^@^@^@^@^@^@^@^@^@^

Question

I have a application server for network operations written with Java based on Apache Mina. Recently I encounter a strange behavior in my log files. I noticed that the log file is full of @^@^@^@^@^@^@^@^@^@^@^@^.... characters. I mean those unexpected characters are vast amount of as such the log file gets hundreds of GB in a couple of hours! I have no clue about this problem and it is almost impossible to google it. What could be the reason? Are those set of characters any familiar to anybody?

I can give more details about the application if needed.

Thanks in advance.

Augment

The messages are possibly a bug in the code doing the logging or, as i've experienced, a malicious attempt to crack the app. – Biathlon

Answer 1

Those characters are null characters (NUL, ASCII value 0) in caret notation.

In caret notation for control characters the null character is ^@.

Johnstone

If you are using vim, try ":set nobomb" to display their real nature – Exterminatory