Trojan.Swifi?

Hi, everyone. I'm currently running NIS 2014 on a Windows Vista computer. I just realized that Norton has managed to "remove" and "quarantine" this Trojan.Swifi, also showing up in the program as vip_117[1].swf, a total of five times in the last twenty four hours. I don't know where this came from or what to do about it, or if Norton truly removed it. If it removed it, why does it keep appearing? Is it a false positive? I checked the forum with no luck for results. Would it be a good idea to run Norton Power Eraser? Thanks, Gina