Transient execution attacks, also known as speculative execution attacks, have drawn much interest in the last few years as they can cause critical data leakage. Since the first disclosure of Spectre and Meltdown attacks in January 2018, a number of new transient execution attack types have been demonstrated targeting different processors. A transient execution attack consists of two main components: transient execution itself and a covert channel that is used to actually exfiltrate the information.Transient execution is a result of the fundamental features of modern processors that are designed to boost performance and efficiency, while covert channels are unintended information leakage channels that result from temporal and spatial sharing of the micro-architectural components. Given the severity of the transient execution attacks, they have motivated computer architects in both industry and academia to rethink the design of the processors and to propose hardware defenses. To help understand the transient execution attacks, this survey summarizes the phases of the attacks and the security boundaries across which the information is leaked in different attacks.This survey further analyzes the causes of transient execution as well as the different types of covert channels and presents a taxonomy of the attacks based on the causes andmore »
Online Detection of Spectre Attacks Using Microarchitectural Traces from Performance Counters
To improve processor performance, computer architects have adopted such acceleration techniques as speculative execution and caching. However, researchers have recently discovered that this approach implies inherent security flaws, as exploited by Meltdown and Spectre. Attacks targeting these vulnerabilities can leak protected data through side channels such as data cache timing by exploiting mis-speculated executions. The flaws can be catastrophic because they are fundamental and widespread and they affect many modern processors. Mitigating the effect of Meltdown is relatively straightforward in that it entails a software-based fix which has already been deployed by major OS vendors. However, to this day, there is no effective mitigation to Spectre. Fixing the problem may require a redesign of the architecture for conditional execution in future processors. In addition, a Spectre attack is hard to detect using traditional software-based antivirus techniques because it does not leave traces in traditional log files. In this paper, we proposed to monitor microarchitectural events such as cache misses, branch mispredictions from existing CPU performance counters to detect Spectre during attack runtime. Our detector was able to achieve 0% false negatives with less than 1% false positives using various machine learning classifiers with a reasonable performance overhead.
- Award ID(s):
- 1763793
- Publication Date:
- NSF-PAR ID:
- 10098124
- Journal Name:
- Proceedings of the 30th International Symposium on Computer Architecture and High Performance Computing (SBAC-PAD 2018)
- Sponsoring Org:
- National Science Foundation
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In early 2018, Meltdown first showed how to read arbitrary kernel memory from user space by exploiting side-effects from transient instructions. While this attack has been mitigated through stronger isolation boundaries between user and kernel space, Meltdown inspired an entirely new class of fault-driven transient-execution attacks. Particularly, over the past year, Meltdown-type attacks have been extended to not only leak data from the L1 cache but also from various other microarchitectural structures, including the FPU register file and store buffer. In this paper, we present the ZombieLoad attack which uncovers a novel Meltdown-type effect in the processor’s fill-buffer logic. Our analysis shows that faulting load instructions (i.e., loads that have to be re-issued) may transiently dereference unauthorized destinations previously brought into the fill buffer by the current or a sibling logical CPU. In contrast to concurrent attacks on the fill buffer, we are the first to report data leakage of recently loaded and stored stale values across logical cores even on Meltdown- and MDS-resistant processors. Hence, despite Intel’s claims [36], we show that the hardware fixes in new CPUs are not sufficient. We demonstrate ZombieLoad’s effectiveness in a multitude of practical attack scenarios across CPU privilege rings, OS processes, virtualmore »
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Transient execution is one of the most critical features used in CPUs to achieve high performance. Recent Spectre attacks demonstrated how this feature can be manipulated to force applications to reveal sensitive data. The industry quickly responded with a series of software and hardware mitigations among which microcode patches are the most prevalent and trusted. In this paper, we argue that currently deployed protections still leave room for constructing attacks. We do so by presenting transient trojans, software modules that conceal their malicious activity within transient execution mode. They appear completely benign, pass static and dynamic analysis checks, but reveal sensitive data when triggered. To construct these trojans, we perform a detailed analysis of the attack surface currently present in today's systems with respect to the recommended mitigation techniques. We reverse engineer branch predictors in several recent x86_64 processors which allows us to uncover previously unknown exploitation techniques. Using these techniques, we construct three types of transient trojans and demonstrate their stealthiness and practicality.
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