OpenBGPd: don't announce a specified prefix to a peer

[smartTERRA NOC]

Hi,

I'm sure there is a way to not announce a specified prefix (learned  
via iBGP or OSPF) to a eBGP peer. But I'm not sure what the filter  
line should look like. Could someone give me a push in the right  
direction?

Regards,

Falk