This indicates an attack attempt against an Information Disclosure vulnerability in Schneider Electric Modicon M580.
The vulnerability is caused by a design issue when the vulnerable software handles a crafted Modbus request. It allows remote attackers to retrieve sensitive information within the context of the application, via a crafted Modbus request.
Schneider Electric Modicon M340
Schneider Electric Modicon M580
Information Disclosure: Remote attackers can gain sensitive information from vulnerable systems.
Apply the most recent upgrade or patch from the vendor.