Web 2.0 technologies are gaining momentum worldwide, penetrating in all industries as enterprise 2.0 applications. Financial services are no exception to this trend. One of the key driving factors behind penetration of Web 2.0 into the financial services sector is the “timely availability of information”. Wells Fargo, Merill Lynch and JP Morgan are developing their next generation technologies using Web 2.0 components; components that will be used in banking software, trading portals and other peripheral services. The true advantage of RSS components is to push information to the end user rather than pull it from the Internet. The financial industry estimates that 95% of information exists in non-RSS formats and could become a key strategic advantage if it can be converted into RSS format. Wells Fargo has already implemented systems on the ground and these have started to yield benefits. Financial services are tuning into Web 2.0 but are simultaneously exposing their systems to next generation threats such as Cross site Scripting (XSS), Cross Site Request Forgery (CSRF) and Application interconnection issues due to SOA.
With regard to security, two dimensions are very critical for financial systems – Identity and Data privacy. Adopting the Web 2.0 framework may involve risks and threats against these two dimensions along with other security concerns. Ajax, Flash (RIA) and Web Services deployment is critical for Web 2.0 applications. Financial services are putting these technologies in place; most without adequate threat assessment exercises. Let’s look at threats to financial services applications using Web 2.0.
Cross site scripting with Ajax
In the last few months, several cross-site scripting attacks have been observed, where malicious JavaScript code from a particular Web site gets executed on the victim’s browser thereby compromising information on the victim’s system. Poorly written Ajax routines can be exploited in financial systems. Ajax uses DOM manipulation and JavaScript to leverage a browser’s interface. It is possible to exploit document.write and eval() calls to execute malicious code in the current browser context. This can lead to identity theft by compromising cookies. Browser session exploitation is becoming popular with worms and viruses too. Infected sessions in financial services can be a major threat. The attacker is only required to craft a malicious link to coax unsuspecting users to visit a certain page from their Web browsers. This vulnerability existed in traditional applications as well but AJAX has added a new dimension to it.
RSS injection
RSS feeds exist in Web 2.0 data format. This format can be pushed to the web application to trigger an event. RSS feeds are a common means of sharing information on portals and Web applications. These feeds are consumed by Web applications and sent to the browser on the client-side. Literal JavaScripts can be injected into RSS feeds to generate attacks on the client browser. An end user visits a particular Web site that loads a page with an RSS feed. A malicious script – a script that can install software or steal cookies – embedded in the RSS feed gets executed. Financial services that use RSS feeds aggressively can pose a potential threat to resource integrity and confidentiality. RSS readers bundled with applications run by end clients can cause identity thefts if they fail to sanitize incoming information.
Untrusted data sources
One of the key elements of Web 2.0 application is its flexibility to talk with several data sources from a single application or page. This is a great feature but from a security perspective, it can be deadly. Financial services running Web 2.0 application provides key features to users such as selecting RSS feeds, search triggers, news feeds, etc. Using these features end users can tune various sources from one location. All these sources can have different point of origin and are totally untrusted. What if one of these sources injects a hyperlink camouflaged as a malicious JavaScript code snippet? Applications that trust these sources blindly can backfire. Clicking a link can compromise the browser session and lead to identity theft. Dealing with untrusted sources in an application framework is a challenge on the security front.
Client-side routines
Web 2.0 based financial applications use Ajax routines to do a lot of work on the client-side, such as client-side validation for data types, content-checking, date fields, etc. Normally client-side checks must be backed up by server-side checks as well. Most developers fail to do so; their reasoning being the assumption that validation is taken care of in Ajax routines. Ajax has shifted a lot of business logic to the client side. This itself is a major threat because it is possible to reverse-engineer or decode these routines and extract internal information. This can help an attacker to harvest critical information about the system.
Widgets exploitation
Widgets are small components that can be integrated into an application very easily without obtaining actual source code. These widgets are offered as part of larger libraries or created by users and posted on the Internet. It is very tempting to use them to achieve short term goals. It must be kept in mind that it is possible that these widgets can be exploited by an attacker if they are poorly written. If financial applications use widgets then it must be made a focal point for analysis. Any weak spot in this widget can lead to script injection on the browser side. It is imperative to analyze the source code of the widget for viruses, worms or possible weaknesses.
Web Services enumeration
Web Services are picking up in the financial services sector and are becoming part of trading and banking applications. Service-oriented architecture is a key component of Web 2.0 applications. WSDL (Web Services Definition Language) is an interface to Web services. This file provides sensitive information about technologies, exposed methods, invocation patterns, etc. that can aid in defining exploitation methods. Unnecessary functions or methods kept open can spell potential disaster for Web services. Web Services must follow WS-security standards to counter the threat of information leakage from the WSDL file. WSDL enumeration helps attacker to build an exploit. Web Services WSDL file access to unauthorized users can lead to private data access.
XML poisoning and Injections
SOAP, XML-RPC and REST are the new standard protocols for information-sharing and object invocation. These standards use XML as underlying sources and financial applications use these standards for client-to-server or application-to-application communication. Not uncommon is the technique of applying recursive payloads to similar-producing XML nodes multiple times. An engine’s poor handling of XML information may result in a denial of services on the server.
Web services consume information and variables from SOAP messages. It is possible to manipulate these variables. For example, if
CSRF with Web 2.0 applications
CSRF allows transactions to be carried out without an end user’s consent, making them one of the most effective attack vectors in financial applications. In Web 2.0 applications Ajax talks with backend Web services over XML-RPC, SOAP or REST. It is possible to invoke them using GET and POST methods. In other words, it is also possible to make cross-site calls to these Web services and in doing so, compromise a victim’s profile interfaced with Web services. CSRF is an interesting attack vector that takes on a new dimension in this newly defined endpoints scenario. These endpoints may be for Ajax or Web services but can also be invoked by cross-domain requests. Key financial transactions cannot depend simply on authenticated sessions, but must take extra care to process information, either by manually validating the password or by using CAPTCHA.
Conclusion
A lot more analysis needs to be done before financial applications can be integrated with their core businesses using Web 2.0. The Web security space is filling up with new attacks as we speak or offering new ways of delivering old attacks – both are dangerous where “monetary transactions” are involved. Here, we have seen just a small set of attacks. There are several other attack vectors with respect to Web 2.0 frameworks. A better threat model is required to undertake a thorough security analysis. Web 2.0 is a promising technology but also one that needs careful coding and usage practices prior to being consumed in applications.
No comments:
Post a Comment