memory system, error, critical

Hello
I just had an MT accredited person helping me to check through the system if all was ok and update the RB 960 PG OS and the cAP ac’s.
Looking at the logs now I see this error:
login failure for user support(this is the ISP) from 192.168..*** via winbox
Is there a way to deal with this so it does not create a huge log file? It seems automatic and is lodged every 2-3Min.
Thanks in advance