[Exim] Filtering Random Letters In Subject

Hello,

I am trying to find out how to filter messages with random letters in the
subject for example:

Subject: zaejhvdnxg- Tight Ones 1799424767

As you can see this random letter string exists. About 1 and a half years
ago i saw a thread of messages which discussed this but i can not find it
anymore.

I am trying to use the Exim Filter command to filter these emails out, as
almost 98% of them are spam.

Can anybody help me with this.

Thanks in advance

Kamesh