This video explains how to create a physical barrier to prevent rodents from entering your home. We just purchased a home built in 1946 with a few additions added to the main building. It was pretty easy to identify entry points for the rodents. If you have a similar house with this issue, take a look in the crawl space, all the way around the perimeter of your home, soffits, around windows, along gutters, look for tree branches hanging near the roof. Loose or damaged fascia boards can also be a point of entry into the attic for rodents and small critters (rats, mice, squirrels, etc...)
It's always best to treat the cause and not the symptom, so focus your energy on physical blocks instead of traps and poison. Listening to an endless stream of rats dying in your attic while you are trying to sleep is not the most fun you'll ever have.... The satisfaction of knowing they have no way to enter your home will make you sleep much better at night! Do all of your repairs during the day while the rodents are out and about. If you have any stuck in your home after putting up physical blocks then it is time to lay traps.
As mentioned previously, we have just moved in and this has been our top priority since we first heard them in the attic. If you let something like this go on the damage done to your home can be enormous. If you can, check all electrical wires in your crawl space and attic for teeth marks or chewed insulation and have any damaged wires replaced immediately.
All supplies I purchased for this came to under $20. This could literally save you $1000's of dollars, if not more!
Good luck, and happy patching!