Don't the Death Eaters know that Snape's a spy?

[jenniferstmatt]

No: HPFGUIDX 106588

I am new at this, so please forgive me if this is an old or much 
discussed question - I did not see it in the FAQs.

At the end of Goblet of Fire, Voldemort summons the Death Eaters.  
They form a circle, and, while he doesn't mention him by name, 
Voldemort indicates that one of the six who are missing has left him 
forever and will, of course, be killed.  Wouldn't Voldemort have 
told the remaining Death Eaters who it is who has left his service 
forever?  Why hasn't an attempt been made on Snape's life?  Snape 
admits to Harry that it is his job to know what Voldemort is telling 
his Death Eaters (Occlumency lesson, Order of the Phoenix) - are the 
Death Eaters feeding him bad information?

Jen