The following are snippets of Peering Policy Clauses found in the Peering Rules of the Road - A Brief Study of Peering Policies study.  Clauses were categorized and put into rough categories for comparison.

Here are the clauses we categorized as requirements for Route Filtering

Excerpts from Peering Polices

Filtering

Peers are expected to filter their clients to reject both unauthorized BGP announcements as well as IP datagrams with invalid source addresses. – Speakeasy

Both parties shall make every reasonable effort to restrict the transmission of Denial of Service attacks and packets with forged source addresses from their network. – InterNap

#  Potential peering partners must enforce strict filtering policies to prevent route leaks. – NAC

Applicant must filter route announcements from their customers by prefix. – Comcast

#  Applicant must use prefix-list filters on customer links – tinet

Peers must enforce routing integrity by means of filters to their customers. – LambdaNet

#  Peers are expected to filter their clients to reject both unauthorized BGP announcements, aggregate prefixes announced as well as filter their prefixes to deny IP datagrams with invalid source addresses.—OpenAccess

Must demonstrate and enforce strict filtering policies to prevent improper announcements – Charter

Potential peer must demonstrate and enforce strict filtering policies to prevent improper announcements. – Cablevision

Both parties must demonstrate and enforce strict filtering policies to prevent route leaks. – WVFiber

Peer must filter route announcements from its customers by prefix. – AT&T