Quantifying XSS – Why Merchants Won't Fix Their Cross-Site Scripting Vulnerabilities

Posted by Brett Hardin on 2nd June 2009

Reading time: 3 – 5 minutes

Photo: bweech

Photo: bweech

From previous articles, you should be aware that Cross-Site Scripting (XSS) is an issue that is not going away any time soon.

Unlike it’s buzzword predecessor, SQL injection, Cross-Site Scripting is a difficult vulnerability to quantify. What is the risk of not resolving a Cross-Site Scripting vulnerability in your web application?

If you have recently gone through a web application assessment, the report most likely indicates the risk factor of having XSS is high. But, what evidence does the report writer have to support this statement?

Basic security teaches us that risk can be quantified as:

Risk = (Probability of the event occurring) x (The impact if the event occurs)

To support the consultants statement, we would need to identify the probability of an attacker using a Cross-Site Scripting vulnerability as an attack vector and what the impact is, if the user is exploited.

Impact
It is important to realize that XSS is a means, not an end. XSS is simply a transportation mechanism. It is used to facilitate the actual attack which could be system compromise or stealing a users session. The only limitation on XSS is that it operates in a browser environment.

Do to the numerous things an attacker can do with XSS, it is hard to quantify an impact for all XSS vulnerabilities. Since XSS has different severities in regards to impact, an organization should always choose the impact that is most severe. In other words, the worst-case-scenario.

If a user is exploited through an XSS attack, an organization can assume the attacker is doing the most damaging thing imaginable. Therefore, if a user is compromised from XSS, the impact is high.

Photo: stopnlook

Photo: stopnlook

Probability of the Attack Occurring
We have now identified that the impact of Cross-Site Scripting is high. But, what about the probability of it actually occurring?

It is difficult to find evidence of people using Cross-Site Scripting as an an attack vector? There are cases where XSS was used, in conjunction with SQL injection, to insert an offsite iframe into a web page in order to attempt a traditional overflow. Should these attacks be included into the equation for probability of it happening? Since it can be argued that these attacks used SQL injection, and not XSS for propagation, these attacks need to be excluded.

The only evidence I can find is Verizon’s 2009 Data Breach Investigation Report. That document however, doesn’t go into much detail about the specifics of the XSS attack.

Due to the lack of overwhelming evidence, XSS currently is not a common attack method. The probability of a Cross-Site Scripting attack occurring is low.

Cost-Benefit Justification of Fixing Cross-Site Scripting
Since it is difficult to quantify the cost of having an XSS, it is just as difficult to do a cost-benefit analysis on fixing XSS vulnerabilities.

Why should merchants spend money on fixing their XSS vulnerabilities when there is no supporting evidence of attacks occurring?

Until more web applications are compromised through XSS vectors and there is more evidence to support this happening, not much security budget will go towards fixing Cross-Site Scripting vulnerabilities.

Update: StrongWebMail was hacked using XSS. StrongWebMail paid out $10,000 for being breached. This has brought some media attention towards the issue.

2Jun

What Motivates Hackers?

Posted by Brett Hardin on 27th May 2009

Reading time: 4 – 6 minutes

Photo: Kristin Bradley

Photo: Kristin Bradley

Attackers are motivated by multiple factors. Previously, “experts” believed most attackers were social outcasts who were writing malicious software out of their parent’s basement. These attackers were not driven by any particular motive. They were more driven by the problem-solving aspect. They wanted to know if they could do it. This idea that attackers are socially inept kids based in the United States is quickly becoming inaccurate.

Most security articles are focused on the means of the attack. They don’t address what attackers are actually after.

The four motivating factors for attackers that have been identified are:

  1. Financial Gain
  2. Notoriety
  3. Political
  4. Vengeance

Financial Gain
Hacking, Malware, and Worm Creation is a money making opportunity. Worms, such as Conficker, are being tied to organized crime based in Soviet republics.

The tightly managed criminal organizations behind such scams—often based in Russia and former Soviet republics—treat malware like a business. They buy advanced code on the Internet’s black market, customize it, then sell or rent the resulting botnet to the highest bidders. They extend the worm’s life span as long as possible by investing in updates—maintenance by another name. This assembly line–style approach to crime works: of all the viruses that Symantec has tracked over the past 20 years, 60 percent of them have been introduced in the past 12 months.

This shouldn’t be surprising. If criminals have no problem killing another human and taking their wallet, why would they have problems stealing massive amounts of money electronically?

However, organized criminals aren’t the only attackers driven by financial gain. There is also evidence of financially driven attackers being petty criminals. These are the types that don’t have a great understanding of what they are doing. They can be found on websites specifically setup for trading credit card numbers or other Personally Identifiable Information (PII). Some researchers, such as Rios and Dhanjani, have done research into this subgroup. What Motivates Hackers?

Notoriety

There is still evidence of hacking for notoriety. Most of these attackers are the “13-19″ year old kids described above. The reason these individuals attack systems is driven by their want to become famous.

A recent example is the Mikeyy worm created by Michael Mooney of StalkDaily. This sub-group usually will justify their attacks by stating, “I wanted to bring awareness to the problem.” This is a constructed answer but demonstrates their want to become famous. They are clearly stating, they were the ones who wanted to bring awareness to the issue. These attackers typically have a Robin Hood type mentality of bringing knowledge to the uninformed.

Political
These attackers are politically focused or driven by political means. This group includes “hacktivists” and foreign nationals driven to cause damage to an enemy country. Examples of these attacks are the Titan Rain and more recently Power Grid hacking.

Political motivation is frightening. Many countries will not deter attackers from hacking a foreign country. In addition, law enforcement has a hard time tracking down or arresting these type of attackers due to the lack of cooperation of foreign countries.What Motivates Hackers?

Vengeance

These attackers are the most dangerous. They will attack people who have somehow made them upset. Their driving factor is causing as much pain as possible for their victim.

These attacks typically target an ex-girlfriend or a celebrity. These are the electronic equivalent of breaking someones windshield. There is nothing that can really be done to prevent it other than to stop using the Internet.

27May

5 Key Factors of Complexity

Posted by Brett Hardin on 20th May 2009

Reading time: 2 – 3 minutes

5 Key Factors of Complexity

Brian J. Truskowski, General Manager of Internet Security Systems (ISS), gave a keynote presentation at RSA 2009. His talk touched on an interesting topic that he referred to as the “5 Key Factors of Complexity.”

He identifies that the key cause of compromise is human nature; the ability that humans are susceptible to social engineering. Instead of focusing on securing systems, Mr. Truskowski argues that we should design systems that are “resistant to human frailty.” He goes on to state, that designing these systems (by reducing complexity) is difficult.

According to Mr. Truskowski, the 5 key factors of complexity and the key to designing these systems are:

  1. Threats
  2. Compliance
  3. Technology
  4. Economics
  5. Business Needs

Contrary to security, Businesses have to keep focused on all of these factors or they will be unsuccessful. Vendors however, are according to Mr. Truskowski, only focused on one of these factors… Threats. He argues, If an enterprise doesn’t focus on compliance, they are fined. If a business doesn’t focus on business needs, the business can’t change.

“It’s like building the titanic. The ship’s designers optimized around being able to withstand collisions at the sacrifice of maneuverability. There have been many theories over the years over why the Titanic sank, from Brittle steel to sub-standard rivets. But, in reality, it is obvious why the Titanic sank. It couldn’t get out of the way of the iceberg. The Titanic’s designers focused on size, strength, resilience, and luxury but not on maneuverability.”

I think Mr. Truskowski’s talk was the hidden gem at RSA. It is an interesting idea for security vendors to begin focusing on things other than threats. Of course, if the idea gets legs, it will be 10-15 years before any change occurs. It is great to see people thinking holistically about security.

The video/webcast can be seen here: (5 Factors of Complexity starts at 19:49)

20May