denial of service attacks

DoS
Denial of Service attacks

An attack designed to bring the network to a halt by flooding it with useless traffic.

Directory Harvesting Attacks

the "Brute Force" directory harvest attack:
a Spammer sends email to every conceivable username @yourdomain

  • bandwidth to your mailserver is consumed by thousands of the bogus incoming messages
  • most mailservers reject email sent to an invalid username with a "user not found" message, which is
     returned to the sender (the Spammer, in this case)
  • bandwidth from your mailserver is consumed by thousands of "user not found" replies
  • the Spammer assumes any email address not drawing a "user not found" reply is in fact a valid address
  • the Spammer creates a list of valid addresses for future Spamming, and sells this list of addreses to others

To make it more difficult for your mailserver to be "harvested" for its directory,
limit the rate of messages (# of messages per minute or per hour) the mailserver accepts.
This makes it more difficult for the attacker to send and get replies to the thousands of
messages that an attack of this sort requires.

You can imagine how beneficial it would be for ISPs such as yahoo.com and comcast.net to prevent
their mailservers from being attacked and harvested in this fashion.

Things you can do:
1. Make sure your mailserver rejects all invalid messages. If the server is configured to forward all invalid
email to a specific account, such as postmaster, a directory harvest attack could fill your free disk space.
2. Put a limit on the frequency of email messages accepted by the mailserver.

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Verizon's Spring Break (-In)

On May 2, 2004, four DS-3 cards were stolen from a Manhattan co-location
facility owned by Verizon Communications at 240 E. 38th St. just after 10:30pm.
The outage affected area customers of Sprint.

***

According to NYC Police, three DS-3 networking cards were stolen from
a Verizon CO at 240 E. 38th St. Sprint lost several cards, Qwest also was
a victim. During the burglary, surveillance cameras were not operational.
Sprint, Qwest, XO Communications, and Looking Glass Networks were
affected by the theft.

*** ***

The co-location floor of a Verizon central office on 38th Street in New York City was burgularized,
leaving a handful of Verizon competitors - specifically Sprint Corp, Qwest Communications,
XO Communications, and Looking Glass Networks - without service for up to an entire day.

New York City Police Department officials pegged the heist at $433,000.
Of the 4 separate doors to the 8th floor co-lo office, the main door lacked a working lock.
All of the network racks that were burgularized were secured with simple Allen wrench bolts.
The building's main entrance security cameras were missing the night of May 2, awaiting upgrade.

51 pieces of networking gear, enough equipment to fill 2 duffel bags, was stolen.

from the NYPD crime report:
Inside of 211 East 37 Street
2004.05.02 23:30 Sunday
Grand Larceny

*** *** ***

Personal Computer Privacy Considerations:

Website History Destruction
Typed URL Destruction
Temporary Internet File Destruction
Search History Destruction
Run Programs History Destruction
Recent Document List Destruction
Media Player History Destruction
Recycle Bin Contents Destruction
Cached File Destruction
Cookie Destruction

http://www.intenseschool.com/

Captchas
Completely Automated Public Turing test to tell Computers and Humans Apart

Methods such as using wavy words in pictures, that require the user to re-type
the word to gain access.
Ticket scalpers use OCR (optical character recognition) software to get around
the Captchas used by ticketmaster.com.