
Industrial Managed
Ethernet Switch
User Manual
錯誤
!
使用
[
常用
]
索
引標籤將
Heading
1,Product Manual
套用到您想要在此處
顯示的文字。
Page
160
of
191
2.20.4 Denial of Service
Denial of Service (DoS) is a malicious attempt to make a machine or network resource unavailable to its intended
users, such as to temporarily or indefinitely interrupt or suspend services of a host connected to the Internet.
EH75XX industrial managed switch is designed so that uses can filter out various types of attack as shown in Denial
of Service setting webpage (Figure 2.186). The followings are some vulnerable attacks that can be prevented by
the EH75XX switch function.
Figure 2.186 Denial of Service Setting Webpage
First is the Local Area Network (LAND) DoS attack
.
LAND is a layer 4 DoS attack in which the attacker sets the
source and destination information of a TCP segment to be the same
.
Specifically, TCP SYN packet is created such
that the source IP and port are set to be the same as the destination address and port, which in turn is set to point
to an open port on a Victim
’s machine
.
A vulnerable machine would receive such a message and reply to the
destination address effectively sending the packet for reprocessing in an infinite loop
.
A vulnerable machine will
crash and freeze due to the packet being repeatedly processed by the TCP stack
.
To enable/disable the protection
against the Local Area Network (LAND) DoS attack, click
Enabled
box on LAND packet (SID=DID) function.
Second is the First Fragment attack.
Thrid attack is called Min TCP Hdr Size attack.
Fourth vulnerability attack is TCP fragmentation attacks also known as tear drop attack, which is targeting TCP
/
IP
reassembly mechanism, preventing them from putting together fragmented data packets
.
As a result, the data
packets overlap and quickly overwhelm the victim
’
s servers, causing them to fail
.
To enable
/
disable the protection
against the TCP fragment DoS attack, click
Enabled
box on TCP Fragment function
.
However, to set the mitigation
method, some certain inputs are needed to set rules of filtering
.
For example, whether the first fragment is allowed
or not and the minimum TCP header size that is allowed
.
In some datalink protocols such as Ethernet, only the first
fragment contains the full upper layer header, meaning that other fragments look like beheaded datagrams
.
No
additional overhead imposed over network because all fragments contains their own IP header
.
Only the first
fragment contains the ICMP header and all remaining fragments are generated without the ICMP header
.