Kerio Tech Firewall6, Administrator'S Manual

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13.5 Scanning of files transferred via Clientless SSL-VPN
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Note: Regardless of what action is set to be taken, the attachment is always removed and
a warning message is attached instead.
Use the TLS connections section to set firewall behavior for cases where both mail client and
the server support TLS-secured SMTP or POP3 traffic.
In case that TLS protocol is used, unencrypted connection is established first. Then, client
and server agree on switching to the secure mode (encrypted connection). If the client or the
server does not support TLS, encrypted connection is not used and the traffic is performed in
a non-secured way.
If the connection is encrypted, firewall cannot analyze it and perform antivirus check for
transmitted messages. WinRoute administrator can select one of the following alternatives:
• Enable TLS. This alternative is suitable for such cases where protection from wiretap-
ping is prior to antivirus check of email.
Hint
In such cases, it is recommended to install an antivirus engine at individual hosts that
would perform local antivirus check.
• Disable TLS. Secure mode will not be available. Clients will automatically assume
that the server does not support TLS and messages will be transmitted through an
unencrypted connection. Firewall will perform antivirus check for all transmitted mail.
The If an attachment cannot be scanned section defines actions to be taken if one or multi-
ple files attached to a message cannot be scanned for any reason (e.g. password-protected
archives, damaged files, etc.):
• Reject the attachment — WinRoute reacts in the same way as when a virus was detected
(including all the actions described above).
• Allow delivery of the attachment — WinRoute behaves as if password-protected or
damaged files were not infected.
Generally, this option is not secure. However, it can be helpful for example when
users attempt to transmit big volume of compressed password-protected files (typi-
cally password-protected archives) and the antivirus is installed on the workstations.
13.5 Scanning of files transferred via Clientless SSL-VPN
Antivirus check is also performed for files transferred between the local network and a remote
client by the Clientless SSL-VPN interface (see chapter 24 ). The SSL-VPN Scanning tab allows to
set advanced parameters for scanning of files transferred via this interface.