SSL 2 was deprecated in 2011. However many devices are manufactured before 2011 and still in use today, and it is impossible to upgrade the software in the device (e.g. cellphones, tablets, PDAs, routers, IP cameras, printers etc.). In designing a network service, it is impractical to limit secure connection to clients with TLS 1.x only, since that would block out a major portion of users.
How insecure would it be, today, if a well-designed network service provides SSL 2 compatibility? Well-designed being, security is provided by multiple approaches, e.g. 2-factor authentication, proper user permission management, encapsulating user inputs in code, auto account locking after a number of failed logins, DMZ properly setup etc. The key factor here is, if SSL 2 is not provided, the service will be completely inaccessible a major portion of devices (30~40%) that are otherwise perfectly functional.
An example would be a corporate email server for daily communications. Sensitive information are never communicated or stored on this server. This server is capable of all SSL/TLS protocols, with an option to disable the weaker protocols.
What exactly are the risks of accepting SSL 2 connections on the server?
EDIT: This is not a question about how SSLv2 is insecure or why it should not be used. It is about the business risk associated with provide SSLv2 as an additional supported protocol for device compatibility. The concerned devices are:
- Perfectly functional.
- Supports only SSLv2. There are no possible software upgrade paths as these are not computers.
- The only other alternative on these devices is a plaintext transmission.
- Represent a majority (or non negligible portion) of the devices using the service.
I'm evaluating the whether to replace all devices, or continue using them but in a relatively insecure manner. It is therefore a business risk management decision. However I must first understand the business risks of providing SSLv2.