Samsung as well as some Dell printers (mfd by Samsung) contain a hard-coded backdoor

This SNMP vulnerability affects thousands of printers. A remote, unauthenticated attacker could access an affected device with administrative read/write privileges and make changes to the device configuration, access sensitive information and possibly leverage further attacks through arbitrary code execution. http://alrt.co/SRJW0A

Takeaway: As a general good security practice, only allow connections from trusted hosts and networks. Restricting access would prevent an attacker from accessing an SNMP interface using the affected credentials from a blocked network location. Continuous monitoring of your network with an IDS and a vulnerability scan will also reveal such a vulnerability and if it’s been exploited.