attack
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... network security communities to
find new and innovative methods to mitigate these types of attacks.
The difficulties in reaching this goal are numerous; some simple
tools ...
... tools already exist to limit the effectiveness and scope of these
attacks, but they have not been widely implemented.
This method ...
...
This method of attack has been known for some time. Defending against
it, however, has been an ongoing concern. Bill Cheswick is quoted in
[2 ...
... 3], at the last minute because there was no way
for an administrator of the system under attack to effectively defend
the system. By mentioning the method, he was concerned about
...
... filtering method discussed in this document does
absolutely nothing to protect against flooding attacks which
originate from valid prefixes ...
... prefixes (IP addresses), it will prohibit an
attacker within the originating network from launching an attack of
...
... attacker within the originating network from launching an attack of
this nature using forged source addresses that do not conform to
...
... urged to implement filtering described in this document to prohibit
attackers from using forged source addresses which do not reside
within a range ...
... filtering is that
it enables the originator to be easily traced to it's true source,
since the attacker would have to use a valid, and legitimately
reachable, source address ...
... prefix, 9.0.0.0/8.
o The attacker launches the attack using randomly changing source
addresses; in this example, the source addresses ...
...
o The attacker launches the attack using randomly changing source
addresses; in this example, the source addresses are depicted as
...
... routing tables, and therefore, unreachable. However, any
unreachable prefix could be used to perpetrate this attack
method.
...
... which appears in the global routing table(s). For example, an
attacker using a valid network address ...
... network address could wreak havoc by making
the attack appear to come from an organization which did not, in
fact, originate the attack and was completely innocent. In such
...
... the attack appear to come from an organization which did not, in
fact, originate the attack and was completely innocent. In such
cases, the administrator of a system under attack ...
... attack and was completely innocent. In such
cases, the administrator of a system under attack may be inclined to
filter all traffic ...
... filter all traffic coming from the apparent attack source. Adding
such a filter would then result in a denial of service ...
... legitimate, non-hostile end-systems. In this case, the administrator
of the system under attack unwittingly becomes an accomplice of the
attacker.
...
... of the system under attack unwittingly becomes an accomplice of the
attacker.
Further complicating matters, TCP SYN ...
... ACK packets being sent to one or many hosts which have no
involvement in the attack, but which become secondary victims. This
allows the attacker to abuse two or more systems at once.
...
... involvement in the attack, but which become secondary victims. This
allows the attacker to abuse two or more systems at once.
Similar attacks ...
... attacker to abuse two or more systems at once.
Similar attacks have been attempted using UDP and ICMP flooding ...
... for system diagnostic ports from outside of their administrative
domain to reach their systems. The latter attack (ICMP flooding),
...
... broadcast replication
mechanics. This attack relies on a router serving a large multi-
access broadcast ...
... the target host attempts to reserve resources waiting for a
response. The attacker repeatedly changes the bogus source address
on each new packet sent, thus exhausting additional host resources ...
... of the connection establishment sequence. In this fashion, the
attacker does damage to two systems: the destination target system,
...
... vendors have
modified their software to allow the targeted servers to sustain
attacks with very high connection attempt rates. This is a welcome
and necessary part of the solution to the problem. Ingress filtering ...
...
The problems encountered with this type of attack are numerous, and
involve shortcomings in host software implementations, routing ...
... 12.0.0.0/8
In the example above, the attacker resides within 9.0.0.0/8, which is
provided Internet connectivity by ISP ...
... link of "router 2", which provides connectivity
to the attacker's network, restricts traffic to allow only traffic ...
... source addresses within the 9.0.0.0/8 prefix, and
prohibits an attacker from using "invalid" source addresses which
reside outside of this prefix ...
... source address spoofing, it does not preclude
an attacker using a forged source address of another host within the
...
... filter range. It does, however, ensure that when an
attack of this nature does indeed occur, a network administrator can
be sure that the attack ...
... attack of this nature does indeed occur, a network administrator can
be sure that the attack is actually originating from within the known
prefixes that are being advertised. This simplifies tracking down the
...
... source address spoofing
denial of service attacks. Network service providers and
administrators ...
... service
providers do so as soon as possible. In addition to aiding the
Internet community as a whole to defeat this attack method, it can
also assist service providers ...
... method, it can
also assist service providers in locating the source of the attack if
service providers can categorically demonstrate that their network ...
... The filtering could also, in practice, block a disgruntled employee
from anonymous attacks.
It is the responsibility of all network administrators ...
... It is the responsibility of all network administrators to ensure they
do not become the unwitting source of an attack of this nature.
...
... network
administrators implement ingress filtering, the opportunity for an
attacker to use forged source addresses as an attack methodology will
...
... attacker to use forged source addresses as an attack methodology will
significantly lessen. Tracking the source of an attack is simplified
...
... source addresses as an attack methodology will
significantly lessen. Tracking the source of an attack is simplified
when the source is more likely to be "valid ...
... when the source is more likely to be "valid." By reducing the number
and frequency of attacks in the Internet as a whole, there will be
more resources for tracking the attacks ...
... attacks in the Internet as a whole, there will be
more resources for tracking the attacks which ultimately do occur.
...