31.   The town has been under attack by rebel groups for a week now.

32.   More than two million refugees have fled the area, fearing attack by loyalist forces.

33.   The rose leaves have curled because of an attack by grubs.

34.   He suffered a vicious attack by a gang of white youths.

35.   His family was subjected to a hideous attack by the gang.

36.   The army has come under attack by separatists.

37.   ...a series of copycat attacks by hooligan gangs.

38.   The spray protects plants from attacks by many common pests.

39.   The soldiers tried to neutralize the attack by dividing the invading army.

40.   We need to make our network more secure against attacks by hackers.