A small and quick introduction to ARP poisoning


This article won’t be about something new nor something extraordinary for any experienced computer security or even the average hacker, but since I’ve been ask this question quite often by some of my friends, I decided to explain how to sniff passwords from a network.  Moreover, I’m well aware I haven’t been writing anything for a while, and I want to get back to it once all my personal matters are resolved. I’ll concentrate on WEP wireless networks since they are almost certain to be cracked easily. Although those a deprecated, there are still used in many household as the out-of-the-box default configuration, so it’s still pertinent in my opinion. Then I will explain the ARP (Address Resolution Protocol) poisoning attack, which will be used to intercept packets between the target and the Internet.

Attacking the WEP wireless network

Packets in a WEP network are encryted, so in order to sniff packets off from it, you’ll first need to acquire the WEP key. This can be done easily with a wireless network adapter that supports monitor mode and the aircrack suite. For the adapter, I’m using the Linksys  Compact Wireless-G USB adapter, model no WUSB54GC. Plug your adapter into a USB connector and boot up your machine. Once you have booted up, make sure Backtrack or any other distribution has detected your adapter:

ifconfig rausb0 up

and then put the adapter in “Monitor Mode”

iwconfig rausb0 mode monitor

The goal of a WEP attack is to capture as many initialization vectors (IVs) as possible. IVs are random numbers used with a either 64, 128 and 256-bit key to encrypt a stream cipher. Those are used so that two exact same plain text do not produce the same ciphertext. The problem with WEP is that IVs are very short, and on a busy network, the same vectors get reused quickly. The IV is 24 bit long, therefore there are 16 777 216 possibilities1. Moreover, changing the IV for each packet is optional. The keys are also quite short, therefore opening the possibility of finding the key with some brute force calculation. No matter what is they key length, you will just need more packets.

The WEP protocol then use the randomly generated IV, the WEP key and pass it throught the RC4 cipher to produce a keystream. The keystream is then XORed with the plain text stream to produce the cipher text, as shown in the picture below:

WEP Encryption Schema
WEP Encryption Schema (from Wikipedia)

So basically, if you get many packets with the same Ivs, different ciphertext, you can now try to brute-force the WEP key. And to get those packets, you need traffic on the network. Now if there are already some people connected and surfing the web, you can easily capture packets and replay them to get more IVs, otherwise, you need to generate the traffic yourself.

Once you’ve tell airodump to capture IVs, we will use aireplay to generate more traffic, and therefore capture more IVs quickly. If you look at the airodump screen, you’ll see it capturing packets.

Once you have the key, you can finally start the poisoning process. As you have seen, I have not detailed how to crack a WEP network as it is widely described all over the net. You can find find good video tutorials from InfinityExists here and here. The last 2600 issue also had a good article about it.

The ARP poisoning attack

The concept behind this is simple. ARP is the protocol that maintains network devices tables up-to-date by associating an IP address with a MAC address. The problem with ARP is that it doesn’t really care about who answered, it will gladly update the tables from whoever says so. Most of the time, it won’t even ask. So the idea behind the attack, is to send the client an ARP answer saying “hey, I’m the gateway, send stuff to me” and a second ARP answer to the real gateway saying “hey there, I’m this guy, send me his stuff”. Then you just have to relay the packets between the victim and the gateway.Those schemas are more simply to understand:

Schema of an ARP Poisoning Attack
Schema of an ARP Poisoning Attack

In Linux, the rerouting can be done using the following iptables commands:

iptables -t nat -A PREROUTING -i <interface> -p tcp –dport <port> -j REDIRECT –to-port <redirection port>

iptables -t nat -D PREROUTING -i <interface> -p tcp –dport <port> -j REDIRECT –to-port <redirection port>

I’m showing those commands because you can do a lot with those. Many web applications such as some Flash applications use RTMP (Real-time messaging protocol) to control web applications, which run locally.  Flash server send commands to the application using message. Using those commands, you can filter the packets send or receive from the Flash server. Simply use a sniffer first, then locate which packets you wish to drop, alter or whatever.

For example, some sites gives you samples of live music or videos for 30 seconds, then nag you to pay. Using a sniffer, analyze the traffic and find that RTMP Invoke packet that closes the connection with the server. Code a quick proxy that will let all packets go to the flash application except for the connection closing RTMP packet. Then use the commands above to redirect traffic to your proxy.

00 03 0d 4f c0 6d 00 11  20 a8 32 8b 08 00 45 00 …O.m..  .2…E.
00 b2 7e 52 40 00 78 06  d0 a1 50 4d 74 05 43 c1 ..~R@.x. ..PMt.C.
ab 3e 07 8f d0 d8 9b a6  b0 eb ea 61 49 3d 80 18 .>…… …aI=..
fe 4a 76 52 00 00 01 01  08 0a 00 ef a6 d0 02 43 .JvR…. …….C
f4 32 43 00 00 00 00 00  76 14 02 00 0f 63 6c 6f .2C….. v….clo
73 65 43 6f 6e 6e 65 63  74 69 6f 6e 00 00 00 00 seConnec tion….
00 00 00 00 00 05 02 00  57 32 30 38 20 46 72 65 …….. W208 Fre
65 63 68 61 74 20 61 63  74 69 76 69 74 79 20 74 echat ac tivity t
69 6d 65 6f 75 74 2e 20  49 66 20 79 6f 75 20 77 imeout.  If you w
65 72 65 20 61 20 6d 65  6d 62 65 72 2c 20 74 68 ere a me mber, th
65 20 66 72 65 65 20 63  68 61 74 20 77 6f 75 6c e free c hat woul
64 20 6e 6f 74 20 74 69  6d 65 20 6f 75 74 21 20 d not ti me out!

Example of a RTMP Invoke packet to close a connection.

Of course you could just use Ettercap, which does exactly what have been mentioned above. Start Ettercap with the following:

sudo ettercap -G -W 128:p:25AAAAC18DEADDADA433332B65

This will open the graphical interface (-G), that is if you have installed the GTK interface to Ettercap. -W specify to listen for wireless networks and to use a 128-bit key with key found earlier. I don’t know what the p is really for. You can also use the text mode.


Then select Sniffing > Unified Sniffing > select on which interface you want to sniff. Then start the sniffing: File > Start Sniffing. Now let’s specify which targets you wanna sniff. Go to Hosts > Scan for hosts. That will locate the hosts on the current network. Then popup the hosts list, Hosts > Show Hosts List.

Ettercap - Hosts Found on the Network
Ettercap - Hosts Found on the Network

On the list, add the router to target 2 and the hosts you wanna sniff to target 1. Only one step left: MITM > ARP poisoning.  Select Sniff Remote Connections > OK.

Ettercap ARP Poisoining Options
Ettercap ARP Poisoining Options

Then you wait for users to connect to pages like MySpace or Hotmail etc…and Ettercap will find out the sensitive information for you.

See also:

Wireless Networking, Praphul Chandra, Alan Bensky, Ron Olexa, Daniel Mark Dobkin, David A. Lide, Farid Dowla

RFC 826 – Ethernet Address Resolution Protocol, David C. Plummer, November 1982, http://www.faqs.org/rfcs/rfc826.html

Wired Equivalent Protocol, Wikipedia, http://en.wikipedia.org/wiki/Wired_Equivalent_Privacy

Ettercap, http://ettercap.sourceforge.net/

Both U.S Presidential Campaigns Hacked


Newsweek reports that the computer systems of M. Obama and M. McCain were both hacked by unknown attackers during their campaigns[1]. Very little information is available, but according to Newsweek, the FBI and the Secret Services claimed that several files from the Obama servers had been compromised by a “foreign entity” in midsummer. The same happened to the McCain campaign.

According to the FBI, documents were stole by foreign powers (probably Russia or China) in order to gather information for future negotiations.

But the former director of technology for the 2004 presidential campaign of Rep. Dennis Kucinich expressed skepticism about the claims. Henry Poole from CivicActions, a firm that offers Internet campaign consulting services, said “It’s unlikely that either campaign would have stored sensitive data on the same servers that were being used for public campaigning purposes[2]“.

It is unclear if anyone got compromised at all. If so, why would the FBI and Secret Services report such events? Hopefully there is more to come on this…

See also:

“Hackers and Spending Sprees”, Newsweek, November 5, 2008, http://www.newsweek.com/id/167581/page/1 (accessed on November 6, 2008)

“Both US political campaigns got hacked”, Egan Orion, The Inquirer, November 6, 2008, http://www.theinquirer.net/gb/inquirer/news/2008/11/06/both-political-campaigns-got (accessed on November 6, 2008)

[1] “Hackers and Spending Sprees”, Newsweek, November 5, 2008, http://www.newsweek.com/id/167581/page/1 (accessed on November 6, 2008)

[2] “Report: Obama, McCain campaign computers were hacked by ‘foreign entity'”, Jaikumar Vijayan, ComputerWorld, http://www.computerworld.com/action/article.do?command=viewArticleBasic&taxonomyName=Cybercrime+and+Hacking&articleId=9119221&taxonomyId=82&pageNumber=1 (accessed on November 6, 2008)

Microsoft: Malware Up 38% in United States in 2008


According to the latest Security Intelligence Report from Microsoft, malicious software installations on computers increased 38% in the U.S for 2008.[1] Also, the number of “High Severity” vulnerabilities detected increased by 13% in the second half of 2007, putting the total of “High Severity” vulnerabilities to 48%.

Downloaders and droppers, accounting for 30% of all malicious software, with around 7 millions computers infected in the United States alone.

And of course, no good Microsoft document would be complete by stating that Vista in more awesome than XP, and therefore the report states that if you own Windows XP SP3, you’re likely to be infected 9 times on 1000 infections, while this number drops to 4 times on 1000 infections for Vista.

“For browser-based attacks on Windows XP-based machines, Microsoft vulnerabilities accounted for 42 percent of the total. On Windows Vista-based machines, however, the proportion of vulnerabilities attacked in Microsoft software was much smaller, accounting for just 6 percent of the total[2].”

Taken from the report:




% Chg.





























Dominican Republic








Saudi Arabia
















Former Yugoslav Republic of Macedonia




























United Arab Emirates












Bosnia and Herzegovina








Table 1.0 – Countries with the Highest Infection Rates[3]

See also:

“Microsoft Security Intelligence Report”, Microsoft, January-June 2008, http://www.microsoft.com/downloads/details.aspx?FamilyId=B2984562-47A2-48FF-890C-EDBEB8A0764C&displaylang=en (accessed on November 4, 2008)

“Les menaces en augmentation de 43%, dit Microsoft”, Marie-Ève Morasse, Cyberpresse, November 3, 2008, http://technaute.cyberpresse.ca/nouvelles/internet/200811/03/01-35773-les-menaces-en-augmentation-de-43-dit-microsoft.php (in French) (accessed on November 4, 2008)

[1] “Microsoft Security Intelligence Report”, Microsoft, January-June 2008, p. 122

[2] Ibid. p. 5

[3] Ibid. p.49

Chinese Cyber Warfare to Gain Military Superiority


Since the 70s, when Deng Xiaoping was the head of China, the People’s Liberation Army tried to modernize itself and cut its size in order to become more efficient. Still, China is still behind when it comes to military even if its defense budget is the second largest after the United States on the planet, with US$57 billion in 2008[1]. According to an article published in Culture Mandala, China could boost its cyber warfare capabilities in order to compensate for their technological backwardness.

It started as soon as in 2003, when it deployed its first cyber warfare units, the “zixunhua budui[2]“. Since, many attacks have been attributed to China, such as Operation Titan Rain in 2003[3]. China hopes that by using asymmetrical warfare, such as information warfare and cyber warfare, it might level other modern armies.

Michael Vickers, Senior Vice President for Strategic Studies at the Center for Strategic and Budgetary Assessments declared that “a Chinese attack on Taiwan could entail special operations and cyber attacks on U.S. regional bases in Japan and South Korea, and might even include cyber attacks on the U.S. homeland that target the U.S. financial, economic, energy, and communications infrastructure[4]“. In the same document, we can read:

“One way to assess this risk is to ask whether a cyber attack by China launched a few days in advance of a clash could prevent U.S. carrier battle groups from deploying to the Taiwan Straits. Launching the attacks too early would create the risk of discovery and countermeasures.[5]

China could boost its cyber warfare capabilities in order to compensate for their technological backwardness
China could boost its cyber warfare capabilities in order to compensate for their technological backwardness

It is clear to me that a nation with a technologically late compared to modern armies have all the advantage to develop asymmetrical warfare. We can assess its effectiveness in Afghanistan and Iraq. And cyber warfare is a perfect way to destabilize modern armies used to technology in their daily operations. But this is far from being easy for both sides, as talented individuals and highly skills hackers are needed to develop this kind of warfare. Terrorists and groups are unlikely to develop a high quality cyber warfare force, although they still can be efficient. China, on the other hand, can and is smart to do it. After all, if a force can disable communications the enemy’s communications networks, such as GPS, emails and phone networks, it can makes a strong army useless. Like a strong man or woman, if the brain can contact the muscle through the nervous system, the body is powerless…

See also:

“How China Will Use Cyber Warfare To Leapfrog in Military Competitiveness“, Jason Fritz, Culture Mandala, Vol. 8, No. 1, October 2008

China’s Military Modernization and Its Impact on the United States and the Asia- Pacific“, U.S.-China Economic and Security Review Commission, 110th Cong, 1st Sess., March 29-30, 2007

[1] “How China Will Use Cyber Warfare To Leapfrog in Military Competitiveness”, Jason Fritz, Culture Mandala, Vol. 8, No. 1, October 2008, pp.29

[2] “Trojan Dragon: China’s Cyber Threat”, John J. Tkacik, Jr., The Heritage Foundation, February 8, 2008, http://www.heritage.org/Research/asiaandthepacific/bg2106.cfm#_ftn6 (accessed November 3, 2008)

[3] “Titan Rain – how Chinese hackers targeted Whitehall”, Richard Norton-Taylor, The Guardian, September 5, 2007, http://www.guardian.co.uk/technology/2007/sep/04/news.internet (accessed November 3, 2008)

[4] China’s Military Modernization and Its Impact on the United States and the Asia- Pacific, U.S.-China Economic and Security Review Commission, 110th Cong, 1st Sess., March 29-30, 2007, p. 2

[5] Ibid. p.144

Bank Account Stealing Trojan Rampaging the Internet


The details of about 500,000 online bank accounts and credit and debit cards have been stolen by a trojan
The details of about 500,000 online bank accounts and credit and debit cards have been stolen by a trojan

BBC News reports that a trojan, labeled Sinowal, has been crawling across the Internet. The Trojan is notorious for stealing bank account details. Sean Brady of RSA‘s security division reports that “more than 270,000 banking accounts and 240,000 credit and debit cards have been compromised from financial institutions in countries including the US, UK, Australia and Poland.[1]” According to Sophos researchers, 14 computers per seconds were infected by Sinowal in 2008[2].

The Trojan is also known as Torpig and Mebroot and has now been discovered 2 years ago, in 2006, which means it has been collecting information for now 2 years. It uses the drive-by download method to download itself, which means it download and install itself without the user’s knowledge. In the case of this particular Trojan, this is done mainly thought malicious links and HTML injection attacks.

The Trojan installs itself on the master boot record and his polymorphic, making it hard to detect and to remove[3]. RSA suspects that the Sinowal had strong ties to a cybercriminal gang known as the Russian Business Network.

[1] “Trojan virus steals banking info”, Maggie Shiels, BBC News, October 31, 2008, http://news.bbc.co.uk/2/hi/technology/7701227.stm (accessed on November 2, 2008)

[2] Idem

[3] “RSA Cracks Down on Legendary Sinowal Trojan“, Richard Adhikari, Internet News, October 31, 2008, http://www.internetnews.com/security/article.php/3782221/RSA+Cracks+Down+on+Legendary+Sinowal+Trojan.htm (accessed on November 2, 2008)

Quebec Launches Campaign Against Identity Theft


Yesterday the ISIQ (Institut de la Sécurité de l’Information du Québec) launched its new campaign to educate citizens computer security and protection of personal information over the Internet. The ISIQ launched a new portal, MonIdentité (in French) containing lots of information for users on how to protect their identity and to identify risks such as phishing, spyware, Trojans and weak passwords. The campaign has been launch by Pierre Arcand, deputy of the Mont-Royal district in Montreal.

“We want the citizens to become their own artisans of their security on the Internet, by adopting a secure behavior.” said M. Pierre Arcand.

The campaign comes amid a declaration from the Chaire de recherche du Canada sur la sécurité, identité et technologie (in French) who reports that in the last 3 years, 314 millions personal files where lost in 976 incidents in Canada and in the United States. Half of them were due to the incompetence of the owning corporation or organization.[1]

This is exactly the kind of initiative we need. Humans are always the weakest link in any security network, therefore educating the population about security is essential. My only fear is that this campaign will largely be ignored by the media and the population, since elections are looming in the province and economic news are still the main topic.

Je Protège Mon Identité - ISIQ Portal
Je Protège Mon Identité - ISIQ Portal

[1] “Pour naviguer sans tracas”, Radio-Canada, October 27, 2008, http://www.radio-canada.ca/nouvelles/societe/2008/10/27/003-securite-informatique.shtml (accessed on October 28, 2008)