10.2 Configuring IP Standard Access Lists
10.2.1 Filtering
Standard access lists allow filtering based on only the source address. The allowable range of standard access lists is 1 to 99. Standard access lists can also be used in other ways such as to limit virtual-terminal connectivity into networking devices. Virtual-terminal connectivity is used to attach to the router in a logical way (such as through serial links).

In the main figure, for example, the router examines only the source address 10.0.0.3 to see whether the packet is restricted by a standard access list.