The remote host is missing an update to netris announced via advisory DSA 372-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20372-1

Shaun Colley discovered a buffer overflow vulnerability in netris, a network version of a popular puzzle game. A netris client connecting to an untrusted netris server could be sent an unusually long data packet, which would be copied into a fixed-length buffer without bounds checking. This vulnerability could be exploited to gain the priviliges of the user running netris in client mode, if they connect to a hostile netris server. For the current stable distribution (woody) this problem has been fixed in version 0.5-4woody1. For the unstable distribution (sid) this problem is fixed in version 0.52-1. We recommend that you update your netris package.