G Glossary
G.1 Active Directory
Microsoft’s implementation of LDAP (Lightweight Directory Access Protocol) on Windows. Active
Directory provides LDAP-like directory services for managing identities and permissions of users
throughout a network. Active Directory is a hierarchical, object-oriented database in which each
object represents a single entity (for example, a user or group).
G.2 adware
Software that displays advertising in your system’s GUI (graphical user interface). Adware is often
installed unknowingly by someone who is downloading and installing free software.
G.3 certificate
Certificates used by the appliance are public key certificates known as X.509 certificates. These
encryption keys are associated with a specific identity or organization, and they allow the identity
of the certificate holder to be verified. Identity verification is an important component of ensuring
secure communication. Without it, it is possible for even encrypted communication to be redirected
or compromised by an untrustworthy third party.
Certificates include information such as the hostname they are to be used with, a digital signature
from a certificate authority, a start date, and an expiry date. To be considered valid, a certificate
must:
■
not yet be expired.
■
have a digital signature from a trusted certificate authority.
■
have a hostname associated with it that matches the hostname of the machine that is using
the certificate.
Note: If your Web Appliance has several hostnames associated with it, it is important that
you ensure the hostname presented to other machines matches your certificate(s) exactly.
By default, the Web Appliance uses what is known as a self-signed certificate. A self-signed
certificate is a certificate that has been signed by the creator of a certificate, rather than by a
third-party CA. This can be useful for providing encryption functionality when verification of the
host’s identity by an external CA is not needed. In this case, the host acts as its own CA. This
can be the case when the Web Appliance needs to verify its identity to a limited set of hosts, such
as communication within a company, or with business partners.
230 | Glossary | Sophos Web Appliance