Security is a global hot topic.

Here in Johannesburg, where security is a very local concern, many have surrounded their homes with high walls, electric fences, security gates and burglar bars. Since 9/11, airports around the globe have introduced security screenings that unnerve even the most ironclad heart. Our home PCs and office networks are protected with firewalls.

It's now not only acceptable, but fashionable to limit access on just about every level of our lives. We know how to keep the burglars, terrorists and spammers out.

Ironically, however, we still remain vulnerable to trespass of a different kind.

A wise man commented: "Jews have always considered it taboo to enter a church, yet nowadays they bring the church into their own homes."

"Church" is more than a place of worship; in a broader sense it symbolizes any idea antithetical to Jewish values.

You could sit in the comfort of your Jewish home, flanked by a silver mezuzah, Shabbat candlesticks and a portrait of your grandfather sporting a flowing white bearded. Press a button on your remote control and you invite people, images, sounds and themes that are contrary to every Jewish value.

"Judges and policeman you shall place at all your gates," the Torah tells us (Deuteronomy 16:18). You could read that at face value—a Jewish town needs to have a judicial system. Or you could approach this line as a Jew should: as a personal lesson. As with every verse in the Torah, if you cannot find the relevant personal lesson, you have missed the larger point.

Let's read that sentence again, with different emphasis this time: "Judges and policemen you shall place on all your gates." Your gates are the access points to your soul: your eyes, ears and mouth.

It's important to keep unwanted visitors out of your house; it's just as important to keep them out of your head (and your kids' heads).

We've invested a fortune in physical security, we should at least equal the effort for our spiritual security.