Don't Click That Link!

Why did you just click that link? Most likely you have came to this site by clicking a link from another site. Why did you do that? Did you trust the person who sent you the link? Did you click a link from twitter, facebook, or an email someone sent you?

When you click a link, you are telling your browser, "I trust this person." However, this is not the way we use the internet. We click on links all the time. We click on links from "untrusted" sources. We click links from people we don't know and we even click on URL's that have been modified. On Twitter, a person is much more inclined to click the shortened link http://bit.ly/5hXRW then they are to click http://somewherebank.com/transfer.jsp?amount=1000&to_account=56777564. Even though the shortened link could redirect to the somwherebank.com site.

But, why would someone trick you into clicking a cleverly disguised link? The site that you are redirected to may seem harmless. It could also be extremely malicious.

What happens if this page, (the one you are currently viewing), was filled with Cross-Site Request Forgery (CSRF) links? This web page could be setup with all types of malicious intent. However, you didn't know that when clicking the link. Now, it is too late.

If this site did have Cross-Site Requests, I could do things such as:

• Change the password on your facebook account
• Transfer the money from your online bank account to another account
• Enact trades from a financial institution such as E*Trade

The sites that I exploit would have to be vulnerable to CSRF. But researchers, such as Mike Bailey and Russ McRee, are constantly finding CSRF vulnerabilities in web applications.

An example of how clicking links from untrusted sources is never good was demonstrated in Billy Rios and Nitesh Dhanjani, Bad Sushi talk. In their presentation they described sending phishers a word document stating their account numbers were inside. They sent this email to 25 known phishers. 10 of the phishers opened the word document and were presented with this. In additon, there was another link that said, "Actually, my account information is here." 3 of the 10 clicked on that link. Even the phishers click links they shouldn't.

What should be done? Who knows. It is human nature to trust people and we can't get things done if everytime someone sends us a link we open up a VMware image to view a link. So continue using the Internet the way you have been and remember, "These aren't the droids your looking for."

Graph Theory: Analyzing Social Networks

Social networking applications are among the most popular websites that are used on the Internet. Facebook.com and myspace.com are both in the top 20 most visited pages on the internet. According to Alexa, 17% of global internet users visit facebook.com on a daily basis.

How can attackers use the abundant amounts of information that is available on these websites to aid in their attacks?

One method is by analyzing a victims social network using network analysis.

Network analysis is a way to infer information from the social connections that someone makes. An attacker could use a social applications data set to:

• identify positive and negative relationships
• identify their victims mood
• identify individuals that are most influential in a group

By assigning people and organizations to nodes and linking nodes based on relationships, attackers can begin to infer information from these social graphs.

Who is the Most Influential?
It is beneficial for an attacker to know who is the most influential person in their victim's social network. Constructing a malicious instant message or email that requires user intervention (think Reflective Cross-Site Scripting) will have a higher success rate, if it is sent from the victim's most influential friend.

In order to analyze the victim's social network from an influential perspective, the attacker begins by constructing a graph with the victim in the center and each of the victim's friends as node off of the victim.

In this example, Sam is the attacker's target. Sam has five friends, Alice, Bart, Charlie, Dave, and Ed. This would create a star graph that would look like this.

The next step is for the attacker to analyze the connections between Sam's friends. The attacker identifies that Alice communicates with Bart on a regular basis, so a link is made between Alice and Bart.

It is also easier for the attacker to understand who is the most influential by assigning a value to each vertice. Alice and Bart's vertice would change from 0 to 1, since they know one of Sam's friends. In this example, we have made the vertice larger and assigned it a number. Once the social network is analyzed the attacker will have a graph similiar to this.

Since Ed knows 3 of Sam's friends, it can be infered that Ed is the most influential in Sam's network. If an attacker wanted to send a malicious instant message or email to Sam, the attacker would have the highest rate of success if the malicious message was from Ed.

This is a simple example. In reality, social networks are vastly more complicated. However, with the use of certain API's an attacker could use network analysis to his benefit.

An XSS Primer - Understanding Cross Site Scripting

If it hasn't already, Cross-Site Scripting (XSS) will soon be replacing SQL injection as the new buzzword in the security sector.

XSS will continually be a topic on this blog as well as others [1],[2],[3],[4]. Due to this fact, I think a primer would be a good idea for those who don't know or understand this problem.

Many articles have been written about Cross-Site Scripting and if you want to have a better understanding of the problem, I suggest you read those documents (Links at the bottom of the post).

Basically, There are 3 types of Cross-Site Scripting:

1. Stored/Non-Reflective/Persistent Cross Site Scripting (User visits the XSS'ed page)
   
2. Non-Stored/Reflective/Reflected Cross Sited Scripting (User clicks a link that embeds the script into the loaded page)
   
3. DOM Based Cross Site Scripting (please read this article)
   

All of these names make it confusing for a first timer to understand XSS. There really should be a better web application security standards organization. Here is a breakdown of Persistent XSS and Reflective XSS. These are the big two that most people talk about when they are referring to Cross Site Scripting. If you understand these well, you will be able to participate in 90% of XSS conversations.

Persistent Cross-Site Scripting
Persistent XSS is arguablly more dangerous than reflective XSS. This attack embeds the malicious script permenatly into the web application. The script will then wait until people access the page it is located on.

Here is an attack using Persistent Cross-Site Scripting:

1. The victim visits a website they trust, amazon.com.
2. A script has been inserted by an attacker on a page they happen to visit while on amazon.com.
   
3. The script executes in the context of amazon.com.
4. The victim is then compromised.
   

Note: Obviously, someone can increase the chances of the victim visiting this page (step 2) through social engineering, phishing, etc.

Reflective Cross-Site Scripting
These are the ones the media usually reports on. [1],[2],[3]. In this attack, some type of social engineering is involved for the attack to be successful.

Here is an attack, using Reflective Cross-Site Scripting:

1. The victim gets an email/Instant Message that contains a link.
2. The victim clicks the link. (Requires User Intervention)
   
3. A script has been inserted by an attacker on the page they then visit.
   
4. The script executes in the context of that site.
   
5. The victim is then compromised.
   

Note: I want to reitterate that this attack requires some type of user intervention (step 2).

Why is Cross-Site Scripting Bad?
Cross-Site Scripting can lead to all sorts of different exploits, including system compromise. For an attacker to do this, they need to break out of the browser's context. We have seen examples that breaking out of the browser is not that hard to do.

In addition, an attacker can also establish a bi-directional channel using iframes. This creates a man-in-the-middle attack. The attacker can then intercept key strokes, use the victim as an intranet portscanner, and even stealing creditials. The attacker is only limited by their knowledge of scripting.

Example of a bi-directional channel

Hopefully, this gives you a better understanding of Cross-Site Scripting. Feel free to leave comments if you don't understand something and I will address it in the article.

Additional Resources:
Cross-Site Scripting (XSS) FAQ
OWASP Guide to XSS
XSS tutorial
XSS Video Tutorial (via youtube)
XSS Attack API

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 Titatic'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)

http://media.omediaweb.com/rsa2009/webcast.htm?id=3_1

Verizon's 2009 Data Breach Investigation Report

Verizon's annual data breach investigation report came out last week, and I finally had a chance to read through it. I read others security bloggers synopsis of it but none of them seemed to point out anything that was interesting to me.

Here is the interesting bit that I found: Verizon actually recorded someone using XSS as an attack vector.

Typically, it is very difficult to find anything online that points to people using XSS maliciously. Most of the time, XSS is used to increase page views (recent Mikeyy worm) or for popularity (Sammy Worm).

We, the security community, now have some type of hard evidence to explain how XSS could potentially be an issue for companies. Is this enough to bring awarness to management?


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