Countering Targeted File Attacks Using LocationGuard

1 Serverless distributed computing has received significant attention from both the industry and the research community. Among the most popular applications are the wide area network file systems, exemplified by CFS [4], Farsite [1] and OceanStore [12]. These file systems store files on a large collection of untrusted nodes that form an overlay network. They use cryptographic techniques to secure files from malicious nodes. Unfortunately, cryptographic techniques cannot protect a file holder from a Denial-of-Service (DoS) or a host compromise attack. Hence, most of these distributed file systems are vulnerable to targeted file attacks, wherein an adversary attempts to attack a small (chosen) set of files by attacking the nodes that host them. This paper presents LocationGuard − a location hiding technique for securing overlay file storage systems from targeted file attacks. LocationGuard has three essential components: (i) location key, consisting of a random bit string (e.g., 128 bits) that serves as the key to the location of a file, (ii) lookup guard, a secure algorithm to locate a file in the overlay network given its location key such that neither the key nor the location is revealed to an adversary, and (iii) a set of location inference guards, which refer to an extensible component of the LocationGuard. The basic core of this component includes four pluggable inference guards: (a) lookup frequency inference guard, (b) end-user IP-address inference guard, (c) file replica inference guard, and (d) file size inference guard. The combination of location key, lookup guard, and location inference guards makes it very hard for an adversary to infer the location of a target file by either actively or passively observing the overlay network. In addition to traditional cryptographic guarantees like file confidentiality and integrity, LocationGuard can be used to mitigate Denial-of-Service (DoS) and host compromise attacks by constructing an efficient file access control mechanism, while adding almost zero performance overhead and very minimal storage overhead to the overlay file system. Our experimental results quantify the overhead of employing LocationGuard and demonstrate its effectiveness against DoS attacks, host compromise attacks and various location inference attacks.