Why mysql max_allowed_packet reset to 1m automatically

Question

I set

SET GLOBAL max_allowed_packet=16777216; 

and also

[mysqld]
max_allowed_packet = 16M

I checked the max_allowed_packet through below command

SHOW VARIABLES LIKE 'max_allowed_packet';

and the value is = 16777216

But after some days max_allowed_packet automatically reset to 1M.

Answer 1

i am pretty sure that your are hacked. i had the same problem for months. i opened general_log and finally found some codes:

   connect root@someipaddress on
   Query select 0x4D5A900..........(verylong)
   Query select sys_exe('cmd /c  c:/windows/nbvqc4.vbs')
   .........
   set global max_allowed_packet 1024
   ........

suggestion: change your root password.