I do recommend the use of St. Benedict's medal, also called the Cross of St. Benedict. http://www.liturgialatina.org/benedictine/stbenmedal.htm

My personal experience tells me that it works (at least) on the etheric level, likely in the astral and above. Source one with good metal though, it may break/corrode when under attack otherwise. You also want to have it blessed by a knowledgeable priest too, the difference is noticeable.