Well, let us hope it is only more overhead. After the attacks on US embassies last week, a number of strategic information organizations were commenting that US owned industrial sites will be next. This threat may not be limited to out-of-country sites, either.
Now I have been to developing countries where there are one or two guards standing around the entrance with sixty year old chrome plated Winchester Model 12 shotguns. This is not the kind of security that will be required. The terrorists of today can overwhelm this in seconds. No, you are going to need an entire security assessment. Your facility will need physical fence, sophisticated motion detection cameras, alarms and, most expensive, trained and heavily armed security personnel.
And, of course, cyber attacks already occur daily.
What domestic sites are vulnerable? Any refinery. An industrial processing cluster, such as Pasadena, Texas (don't worry, I am not giving away any secrets, the bad guys figured this out long ago). But I can also think of two or three large, remote papermills whose partial destruction could completely upset commerce throughout the country. Yes, I said papermills.
Outside the US? Everything is subject to attack.
If you have not done a security and threat assessment in the past year, you need to do so. Now.