They are commonly deployed by autonomous systems (AS) to offer access to their routing infrastructure in order to facilitate debugging network issues.
[1] A Looking Glass server is accessed remotely for the purpose of viewing routing information.
[1] Looking glasses are web scripts directly connected to routers' admin interfaces such as telnet and SSH.
[1] These scripts are designed to relay textual commands from the web to the router and print back the response.
A 2014 paper demonstrated the potential security concerns of Looking Glass servers, noting that even an "attacker with very limited resources can exploit such flaws in operators' networks and gain access to core Internet infrastructure", resulting in anything from traffic disruption to global Border Gateway Protocol (BGP) route injection.