Controlling the data traffic
8.1
Helping protect against unauthorized access
99
UM Config GRS
Release
8.0
09/2019
8 Controlling the data traffic
The device checks the data packets to be forwarded in accordance with defined rules. Data packets
to which the rules apply are either forwarded by the device or blocked. If data packets do not
correspond to any of the rules, then the device blocks the packets.
Routing ports to which no rules are assigned allow packets to pass. As soon as a rule is assigned,
the assigned rules are processed first. After that, the specified standard action of the device takes
effect.
The device provides the following functions for controlling the data stream:
Service request control (Denial of Service, DoS)
Denying access to devices based on their IP or MAC address (Access Control List)
The device observes and monitors the data stream. The device takes the results of the observation
and the monitoring and combines them with the rules for the network security to create what is
known as a status table. Based on this status table, the device decides whether to accept, drop or
reject data.
The data packets go through the filter functions of the device in the following sequence:
DoS … if
permit
or
accept
, then progress to the next rule
ACL … if
permit
or
accept
, then progress to the next rule
8.1
Helping protect against unauthorized access
With this function, the device supports you in helping protect against invalid or falsified data packets
targeted at causing the failure of certain services or devices. You have the option of specifying
filters in order to restrict data stream for protection against denial-of-service attacks. The activated
filters check incoming data packets and discard them as soon as a match with the filter criteria is
found.
The
Network Security > DoS > Global
dialog contains 2 frames in which you activate different filters.
To activate them, mark the corresponding checkboxes.
In the
TCP/UDP
frame, you activate up to 4 filters that only influence TCP and UDP packets. Using
this filter, you deactivate port scans, which attackers use to try to recognize devices and services
offered. The filters operate as follows:
Table 14: DoS filters for TCP packets
Filter
Action
Activate Null Scan Filter
The device detects and discards TCP packets for which no TCP flags
are set.
Activate Xmas Filter
The device detects and discards TCP packets for which the TCP flags
FIN, URG and PUSH are simultaneously set.
Activate SYN/FIN Filter
The device detects and discards TCP packets for which the TCP flags
SYN and FIN are simultaneously set.
Activate Minimal Header
Filter
The device detects and discards TCP packets for which the TCP
header is too short.
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