Chinese downloads overloading my website

Got a note from an ISP today indicating that my website was suspended due to data transfer over-use for the month. (>50G)
It's only the 7th day of the month and this hadn't been a problem in the 6 years they'd hosted the service.
Turns out that three chinese sources had downloaded the same set of files, each 262 times. That would do it.
So, anyone else looking to update bipolar semiconductor, packaging or spice parameter spreadsheets; look at K.A.Pullen's 'Conductance Design Curve Manual' or any of the other bits stored at ve3ute.ca are out of luck, for the rest of the month .
Seems strange that the same three addresses downloaded the same files, the same number of times. Is this a denial of service attack?
RL