它是用来保护~~~免于~~~~的攻击 怎么说

It is used to protect sth/sb against attack (attack 袭击,攻击 在这里做名词使用)
保护 protect
保护....免于.... protect.... from/against....
it is used to ..... 它是被用来....

It is uses for to protect avoid the attack

It is used to prevent...from being attacked by...

it is used to prevent sb./sth. from being attacked by sb./sth

It is used to protect ~ ~ ~ ~ ~ ~ ~ from the attack.