Anonymity levels - applies for http/https proxies only.
* Level 1: No anonymity; remote host knows your IP and knows you are using proxy.
* Level 4: Low anonymity; remote host does not know your IP, but it knows you are using proxy.
* Level 8: Medium anonymity; remote host knows you are using proxy, and thinks it knows your IP, but this is not yours (this is usually a multihomed proxy which shows its inbound interface as REMOTE_ADDR for a target host).
* Level 16: High anonymity; remote host does not know your IP and has no direct proof of proxy usage (proxy-connection family header strings). If such hosts do not send additional header strings it may be considered as high-anonymous. If a high-anonymous proxy supports keep-alive you can consider it to be extremely-anonymous. However, such a host is highly possible to be a honey-pot.
KA means "keep-alive".