They are ALLAH's words and they are very powerful. They are not just dead words.
I have already explained the concept somewhere on this forum, but i will explain it again.
ALLAH has said that Koran will be protected till judgement day and till that day no change will be made to it.
Now for every letter,for every word of Koran, its protected by creatures on duty set by ALLAH. These creatures are called "moakills". They are stronger than jinns but shorter in stature.Their diet is "zikr".
So now some amil/sufi/molvi does some chilla of some ayats or surahs for forty days. The moakills come and tease him at first but, he overcomes their distractions and stays absorbed in zikr of ALLAH(i.e. recitation of those ayats) and completes forty days.
Then whenever he recites those ayats/surah, moakills atonce appear.
Once an amil/molvi/sufi writes a taweez or recites something on a taweez, the moakills atonce appear and he then gives the taweez to the affected person who wears it around the neck and due to those ayats/surah and the associated moakills with them, the cure or effects of taweez starts off.
I have explained it in most simple words, the procedure is not that simple as it sounds and i have excluded some un-necessary steps required in the process also.
Just for informtaion, a black magician uses jinns instead of moakills, because he uses ayats wrongly (read backwards) or thru hindu holy book or any other illegal ways. Then he associates those jinns with the thread or food or any other thing and gives the person to give to next person to harm him.
There is a contradiction in your reply. First the Ayats can't be corrupted because the Quran can't be changed. But people who perform black magic do twist and change the Ayats to harm people or do other negative things. You have to decide yourself if they can be changed or not.
In my knowledge the Quran can't be changed in the way the Bible and other Holy Books have been changed and corrupted and lost their meaning. It can't be done to the Quran because we still have the original copy and there are a dozen million people who know the entire Quran by heart, which is truly a miracle.
Natural disasters occur and people die, houses are destroyed. Sometimes houses burn down. Even houses with inhabitants who own a Quran. The Quran will unfortunately just burn down like the other things in the house. So even If you somehow tie a Quran around your neck, it will not help you when harm comes in your way. Believing that an Ayat around your Neck can help you in any way is illogical. Only Allah SWT can help you If he wishes to help you.