Spectre attacks exploit speculative execution in modern processors to leak confidential information from a victim's memory. These attacks use side-channel techniques to bypass memory isolation and process boundaries. The paper describes practical attacks that combine methods from side-channel attacks, fault attacks, and return-oriented programming to read arbitrary memory from a victim's process. Spectre attacks violate security assumptions underlying software security mechanisms, including process separation, static analysis, containerization, JIT compilation, and countermeasures to cache timing attacks. These attacks pose a serious threat to systems using Intel, AMD, and ARM processors, which are present in billions of devices. Spectre attacks work by tricking the processor into speculatively executing instructions that should not occur during correct program execution. These instructions, called transient instructions, can leak information from the victim's memory. The paper demonstrates attacks using native code and JavaScript, showing how Spectre can violate process isolation and browser sandboxing. The attacks use microarchitectural covert channels, such as cache-based techniques like Flush+Reload and Evict+Reload, to leak information. The paper also discusses how Spectre attacks can exploit conditional and indirect branch mispredictions. For conditional branches, the attacker misleads the branch predictor to execute code that would not otherwise be executed, leaking information. For indirect branches, the attacker uses return-oriented programming to influence the victim's execution path, allowing speculative execution of code that would not normally be executed. The paper shows that Spectre attacks can be implemented on various processors, including Intel, AMD, and ARM. The attacks are orthogonal to Meltdown, which exploits privilege escalation vulnerabilities in Intel processors. Spectre attacks can be used to read memory from non-Intel processors, including AMD and ARM processors. The paper also discusses variations of Spectre attacks, including Evict+Time and Instruction Timing, which use different side-channel techniques to leak information. The paper concludes that Spectre attacks represent a serious threat to modern computing systems, as they exploit vulnerabilities in speculative execution to bypass security mechanisms. The attacks highlight the need for hardware and software solutions to address the security implications of speculative execution.Spectre attacks exploit speculative execution in modern processors to leak confidential information from a victim's memory. These attacks use side-channel techniques to bypass memory isolation and process boundaries. The paper describes practical attacks that combine methods from side-channel attacks, fault attacks, and return-oriented programming to read arbitrary memory from a victim's process. Spectre attacks violate security assumptions underlying software security mechanisms, including process separation, static analysis, containerization, JIT compilation, and countermeasures to cache timing attacks. These attacks pose a serious threat to systems using Intel, AMD, and ARM processors, which are present in billions of devices. Spectre attacks work by tricking the processor into speculatively executing instructions that should not occur during correct program execution. These instructions, called transient instructions, can leak information from the victim's memory. The paper demonstrates attacks using native code and JavaScript, showing how Spectre can violate process isolation and browser sandboxing. The attacks use microarchitectural covert channels, such as cache-based techniques like Flush+Reload and Evict+Reload, to leak information. The paper also discusses how Spectre attacks can exploit conditional and indirect branch mispredictions. For conditional branches, the attacker misleads the branch predictor to execute code that would not otherwise be executed, leaking information. For indirect branches, the attacker uses return-oriented programming to influence the victim's execution path, allowing speculative execution of code that would not normally be executed. The paper shows that Spectre attacks can be implemented on various processors, including Intel, AMD, and ARM. The attacks are orthogonal to Meltdown, which exploits privilege escalation vulnerabilities in Intel processors. Spectre attacks can be used to read memory from non-Intel processors, including AMD and ARM processors. The paper also discusses variations of Spectre attacks, including Evict+Time and Instruction Timing, which use different side-channel techniques to leak information. The paper concludes that Spectre attacks represent a serious threat to modern computing systems, as they exploit vulnerabilities in speculative execution to bypass security mechanisms. The attacks highlight the need for hardware and software solutions to address the security implications of speculative execution.