The LW softw team have apparently discussed size filters. But the problem is if they introduce it, then spam will simply get bigger. Then instead of it being less than 1,000 KB (1 MB), it will then become as large as any file out there. As it is, spamming of fake files is already here. The Junk filter which is a dynamic learning filter, filters out most common spam anyway. It requires a lot of persistence to learn to cope with viruses however. The junk filter only works when the user applies it. Not on its own.