Which versions of SNMP are considered insecure?

SNMPv1 and SNMPv2 are considered insecure due to their reliance on community strings for authentication. In these versions, the community strings function like passwords, but they are sent in plaintext over the network. This lack of encryption means that anyone with access to the network can potentially intercept these strings and gain unauthorized access to the SNMP-managed devices.

Due to these vulnerabilities, SNMPv3 was developed to address these security shortcomings. It includes features such as authentication, encryption, and access control, significantly enhancing the security of SNMP communications. Therefore, SNMPv1 and SNMPv2 are not suitable for environments that require secure management of network devices, making them inherently less secure compared to SNMPv3.

The other options either reference versions of SNMP that are secure (like SNMPv3), or do not pertain to SNMP exclusively, making them less relevant to the question of which versions are deemed insecure.