The group had targeted about 40 firms as part of an international conspiracy to force the closure of Huntingdon Life Sciences (HLS), an animal research laboratory based near Cambridge. The members of Stop Huntingdon Animal Cruelty (SHAC) posted hoax parcel bombs to staff and offices, carried out criminal damage, threatened violence and made abusive phone calls, Winchester Crown Court was told.
The campaign also used tactics such as false allegations of paedophilia against managers of the supply companies, and posting sanitary towels to their homes saying the blood was contaminated with the AIDS virus.
Some employees from firms in Britain, France, Germany, Sweden and Switzerland had "puppy killer" and "scum" daubed on their houses.
The cost of the damage and increased security measures amounted to 12.6 million pounds, the court heard.