Web authentication that is both secure and usable remains a challenge. Passwords are vulnerable to phishing attacks, while physical tokens face deployment obstacles. We propose to leverage the authentication infrastructure of cellular networks to enhance Web authentication. We design WebCallerID, a Web authentication scheme that uses cell phones as physical tokens and uses cellular networks as trusted identity providers. Since WebCallerID requires no user participation during authentication, it prevents security mistakes by users. WebCallerID also prevents rogue websites from replaying authentication assertions or stealing users' identities. We have implemented a prototype of WebCallerID using the OpenID framework. The prototype shows that WebCallerID seamlessly integrates into OpenID-capable Web authentication while avoiding phishing problems in OpenID and simplifying user participation.

The current security model used by web browsers, the Same Origin Policy (SOP), does not support secure cross-domain communication desired by web mashup developers. The developers have to choose between no trust, where no communication is allowed, and full trust, where third-party content runs with the full privilege of the integrator. Furthermore, the SOP has its own set of security vulnerabilities and pitfalls, including Cross-Site Request Forgery, DNS rebinding and dynamic pharming. To overcome the unfortunate tradeoff between security and functionality forced upon today's mashup developers, we propose OMash, a simple abstraction that treats web pages as objects and allows objects to communicate only via their declared public interfaces. Since OMash does not rely on the SOP for controlling DOM access or cross-domain data exchange, it does not suffer from the SOP's vulnerabilities. We show that OMash satisfies the trust relationships desired by mashup authors and may be configured to be backward compatible with the SOP. We implemented a prototype of OMash using Mozilla Firefox 2.0 and demonstrated several proof-of-concept applications.

We present a framework to prevent code injection attacks in MS Windows using Native APIs in the operating system. By adopting the idea of diversity, this approach is implemented in a two-tier framework. The first tier permutes the Native API dispatch ID number so that only the Native API calls from legitimate sources are executed. The second tier provides an authentication process in case an attacker guesses the first-tier permutation order. The function call stack is back-traced to verify whether the original caller's return address resides within the legitimate process. The process is terminated and an alert is generated when an attack is suspected. Experiments indicate that our approach poses no significant overhead.

Malware, software with malicious intent, has emerged as a widely-spread threat to system security. It is difficult to detect malware reliably because new and polymorphic malware programs appear frequently. It is also difficult to remove malware and repair its damage to the system because it can extensively modify a system. We propose a novel framework for automatically removing malware from and repairing its damage to a system. The primary goal of our framework is to preserve system integrity. Our framework monitors and logs untrusted programs' operations. Using the logs, it can completely remove malware programs and their effects on the system. Our framework does not require signatures or other prior knowledge of malware behavior. We implemented this framework on Windows and evaluated it with seven spyware, trojan horses, and email worms. Comparing our tool with two popular commercial anti-malware tools, we found that our tool detected all the malware's modifications to the system detected by the commercial tools, but the commercial tools overlooked up to 97% of the modifications detected by our tool. The runtime and space overhead of our prototype tool is acceptable. Our experience suggests that this framework offers an effective new defense against malware.