Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of SIGA Technologies (Nasdaq: SIGA) jumped 12% in trading today as rumors swirled around the company.

So what: There are rumors the Biomedical Advanced Research and Development Authority -- or BARDA -- is going to award a contract to SIGA soon. Although no solid news is out yet, buyers came to the market in droves and have driven volume to over four times the daily average.

Now what: Buying on rumors is risky business and we've seen pops like this before from SIGA, only to see the stock fall back down to earth. Unless SIGA releases solid news after hours, I would watch from the sidelines. First-quarter results are due out tomorrow, so management should have something to say about a possible contract. If a contract is awarded, it could be a game changer, but I'd like solid word first.

Interested in more info on SIGA Technologies? Add it to your watchlist.