Besides traditional problems such as potential bugs, (smartphone) application clones on Android markets bring new threats. That is, attackers clone the code from legitimate Android applications, assemble it with malicious code or advertisements, and publish these "purpose-added" app clones on the same or other markets for benefits. Three inherent and unique characteristics make app clones difficult to detect by existing techniques: a billion opcode problem caused by cross-market publishing, gap between code clones and app clones, and prevalent Type 2 and Type 3 clones.Existing techniques achieve either accuracy or scalability, but not both. To achieve both goals, we use a geometry characteristic, called centroid, of dependency graphs to measure the similarity between methods (code fragments) in two apps. Then we synthesize the method-level similarities and draw a Y/N conclusion on app (core functionality) cloning. The observed "centroid effect " and the inherent "monotonicity" property enable our approach to achieve both high accuracy and scalability. We implemented the app clone detection system and evaluated it on five whole Android markets (including 150,145 apps, 203 million methods and 26 billion opcodes). It takes less than one hour to perform cross-market app clone detection on the five markets after generating centroids only once.

As part of our search for new antifungal agents from natural resources, 22 C-27 steroidal saponins and 6 steroidal sapogenins isolated from several monocotyledonous plants were tested for their antifungal activity against the opportunistic pathogens Candida albicans, Candida glabrata, Candida krusei, Cryptococcus neoformans, and Aspergillus fumigatus. The results showed that the antifungal activity of the steroidal saponins was associated with their aglycone moieties and the number and structure of monosaccharide units in their sugar chains. Within the 10 active saponins, four tigogenin saponins (compounds 1 to 4) with a sugar moiety of four or five monosaccharide units exhibited significant activity against C. neoformans and A. fumigatus, comparable to the positive control amphotericin B. The antifungal potency of these compounds was not associated with cytotoxicity to mammalian cells. This suggests that the C-27 steroidal saponins may be considered potential antifungal leads for further preclinical study.

No abstract