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VoIP/(802.11g) ADSL2+ (VPN) Firewall Router
Chapter 4: Configuration
70
Intrusion Detection
The router’s
Intrusion Detection System
(IDS) is used to detect hacker attacks and intrusion attempts
from the Internet. If the IDS function of the firewall is enabled, inbound packets are filtered and blocked
depending on whether they are detected as possible hacker attacks, intrusion attempts or other
connections that the router determines to be suspicious.
Blacklist
: If the router detects a possible attack, the source IP or destination IP address will be added to
the Blacklist. Any further attempts using this IP address will be blocked for the time period specified as the
Block Duration
. The default setting for this function is false (disabled). Some attack types are denied
immediately without using the Blacklist function, such as
Land attack
and
Echo/CharGen scan
.
Intrusion Detection
: If enabled, IDS will block Smurf attack attempts. Default is false.
Block Duration:
~
Victim Protection Block Duration
: This is the duration for blocking
Smurf
attacks. Default
value is 600 seconds.
~
Scan Attack Block Duration
: This is the duration for blocking hosts that attempt a possible
Scan attack. Scan attack types include
X’mas scan, IMAP SYN/FIN scan
and similar attempts.
Default value is 86400 seconds.
~
DoS Attack Block Duration
: This is the duration for blocking hosts that attempt a possible
Denial of Service (DoS) attack. Possible DoS attacks this attempts to block include
Ascend Kill
and
WinNuke
. Default value is 1800 seconds.
Max TCP Open Handshaking Count
: This is a threshold value to decide whether a
SYN Flood
attempt
is occurring or not. Default value is 100 TCP SYN per seconds.
Max PING Count
: This is a threshold value to decide whether an
ICMP Echo Storm
is occurring or not.
Default value is 15 ICMP Echo Requests (PING) per second.
Max ICMP Count
: This is a threshold to decide whether an
ICMP flood
is occurring or not. Default value
is 100 ICMP packets per seconds except ICMP Echo Requests (PING).
For
SYN Flood
,
ICMP Echo Storm
and
ICMP flood
, IDS will just warn the user in the Event Log. It cannot
protect against such attacks.
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Chapter 4: Configuration
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Table 2: Hacker attack types recognized by the IDS
Intrusion Name
Detect Parameter
Blacklist
Type of Block
Duration
Drop Packet Show Log
Ascend Kill
Ascend Kill data
Src IP
DoS
Yes
Yes
WinNuke
TCP
Port 135, 137~139,
Flag: URG
Src IP
DoS
Yes
Yes
Smurf
ICMP type 8
Des IP is broadcast
Dst IP
Victim
Protection
Yes
Yes
Land attack
SrcIP = DstIP
Yes
Yes
Echo/CharGen Scan
UDP Echo Port and
CharGen Port
Yes
Yes
Echo Scan
UDP
Dst
Port
=
Echo(7)
Src IP
Scan
Yes
Yes
CharGen Scan
UDP
Dst
Port
=
CharGen(19)
Src IP
Scan
Yes
Yes
X’mas Tree Scan
TCP Flag: X’mas
Src IP
Scan
Yes
Yes
IMAP
SYN/FIN Scan
TCP Flag: SYN/FIN
DstPort: IMAP(143)
SrcPort: 0 or 65535
Src IP
Scan
Yes
Yes
SYN/FIN/RST/ACK
Scan
TCP,
No Existing session
And
Scan
Hosts
more than five.
Src IP
Scan
Yes
Yes
Net Bus Scan
TCP
No Existing session
DstPort = Net Bus
12345,12346, 3456
SrcIP
Scan
Yes
Yes
Back Orifice Scan
UDP,
DstPort
=
Orifice Port (31337)
SrcIP
Scan
Yes
Yes
SYN Flood
Max
TCP
Open
Handshaking Count
(Default 100 c/sec)
Yes
ICMP Flood
Max
ICMP
Count
(Default 100 c/sec)
Yes
ICMP Echo
Max PING Count
(Default 15 c/sec)
Yes
Src IP
: Source IP
Src Port
: Source Port
Dst Port
: Destination Port
Dst IP
: Destination IP
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URL Filter
URL (Uniform Resource Locator – e.g. an address in the form of
or
) filter rules allow you to prevent users on your network from accessing particular
websites by their URL. There are no pre-defined URL filter rules; you can add filter rules to meet your
requirements.
Enable/Disable:
To enable or disable URL Filter feature.
Block Mode:
A list of the modes that you can choose to check the URL filter rules. The default is set to
Always On.
~
Disabled:
No action will be performed by the Block Mode.
~
Always On:
Action is enabled.
URL filter rules will be monitoring and checking at all hours of
the day.
~
TimeSlot1 ~ TimeSlot16:
It is self-defined time period.
You may specify the time period to
check the URL filter rules, i.e. during working hours. For setup and detail, refer to
Time
Schedule
section.
Keywords Filtering:
Allows blocking by specific keywords within a particular URL rather than having to
specify a complete URL (e.g. to block any image called “advertisement.gif”). When enabled, your
specified keywords list will be checked to see if any keywords are present in URLs accessed to determine
if the connection attempt should be blocked. Please note that the URL filter blocks web browser (HTTP)
connection attempts using port 80 only.
For example
, if the URL is
, it will be dropped as the keyword “abcde”
occurs in the URL.
Domains Filtering:
This function checks the whole URL not the IP address, in URLs accessed against
your list of domains to block or allow.
If it is matched, the URL request will be sent (Trusted) or dropped
(Forbidden).
For this function to be activated, both check-boxes must be checked.
Here is the
checking procedure:
1.
Check the domain in the URL to determine if it is in the trusted list. If yes, the connection
attempt is sent to the remote web server.
2.
If not, check if it is listed in the forbidden list.
If yes, then the connection attempt will be
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Chapter 4: Configuration
73
dropped.
3.
If the packet does not match either of the above two items, it is sent to the remote web
server.
4.
Please be note that the completed URL, “www” + domain name shall be specified. For
example
to
block
traffic
to
www.google.com.au
,
enter
www.google
or
www.google.com
In the example below, the URL request for
www.abc.com
will be sent to the remote web server because it
is listed in the trusted list, whilst the URL request for
www.google
or
www.google.com
will be dropped,
because
www.google
is in the forbidden list.
Example:
Andy wishes to disable all WEB traffic except for ones listed in the trusted domain, which
would prevent Bobby from accessing other web sites.
Andy selects both functions in the
Domain
Filtering
and thinks that it will stop Bobby.
But Bobby knows this function,
Domain Filtering
, ONLY
disables all WEB traffic except for
Trusted Domain,
BUT not its
IP address.
If this is the situation,
Block surfing by IP address
function can be handy and helpful to Andy.
Now, Andy can prevent Bobby
from accessing other sites.
Restrict URL Features:
This function enhances the restriction to your URL rules.
~
Block Java Applet:
This function can block Web content that includes the Java Applet. It is to
prevent someone who wants to damage your system via standard HTTP protocol.
~
Block surfing by IP address:
Preventing someone who uses the IP address as URL for
skipping Domains Filtering function.
Activates only and if Domain Filtering enabled.
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VoIP/(802.11g) ADSL2+ (VPN) Firewall Router
Chapter 4: Configuration
74
IM / P2P Blocking
IM, short for Instant Message, is required to use client program software that allows users to
communicate, in exchanging text message, with other IM users in real time over the Internet.
A P2P
application, known as Peer-to-peer, is group of computer users who share file to specific groups of people
across the Internet.
Both Instant Message and Peer-to-peer applications make communication faster
and easier but your network can become increasingly insecure at the same time.
Billion’s IM and P2P
blocking helps users to restrict LAN PCs to access to the commonly used IM, Yahoo and MSN, and P2P,
BitTorrent and eDonkey, applications over the Internet.
Instant Message Blocking:
The default is set to
Disabled.
~
Disabled:
Instant Message blocking is not triggered. No action will be performed.
~
Always On:
Action is enabled.
~
TimeSlot1 ~ TimeSlot16:
This is the self-defined time period.
You may specify the time
period to trigger the blocking, i.e. during working hours. For setup and detail, refer to
Time Schedule
section.
Yahoo/MSN Messenger:
Check the box to block either or both Yahoo or/and MSN Messenger.
To be
sure you enabled
the
Instant Message Blocking
first.
Peer to Peer Blocking:
The default is set to
Disabled.
~
Disabled:
Instant Message blocking is not triggered. No action will be performed.
~
Always On:
Action is enabled.
~
TimeSlot1 ~ TimeSlot16:
This is the self-defined time period.
You may specify the time
period to trigger the blocking, i.e. during working hours. For setup and detail, refer to
Time Schedule
section.
BitTorrent / eDonkey:
Check the box to block either or both Bit Torrent or/and eDonkey.
To be sure you
enabled
the
Peer to Peer Blocking
first.

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