Though Israel had put plans for a ground operation in Gaza on hold Tuesday, one invasion had taken place in Operation Pillar of Defense: the IDF took over Hamas television and radio broadcasts, replacing the regular broadcasts with special bulletins aimed at Gaza residents.

IDF sources said that the messages included information on the success of the Iron Dome system in preventing Hamas missiles from striking Israeli cities, the importance of staying away from Hamas operatives who may be targeted by IDF missiles, and even information on how Gaza civilians can protect themselves during an IDF attack.

Other broadcasts showed clips of the IDF’s successes in killing Gaza terrorists, accompanied by a voiceover urging Gazans to rise up against Hamas, which, it says, has only brought them death and destruction. There are also cartoons, such as a one that shows a telephone ringing, unanswered, with accompanying text telling Gazans that “Hamas has run away and is leaving you hanging on the line,” Channel 10 reported.

The battle has also been played out on cellphones. Islamic Jihad claimed over the weekend that it sent out text messages to 5,000 IDF soldiers and officers warning them to stay away from Gaza, lest “we turn Gaza into a graveyard for you.” Hamas also reportedly interrupted Israel’s Channel 10 and Channel 2 broadcasts on private satellites Tuesday nights for a few seconds, broadcasting propaganda. Israel, meanwhile, has been sending Gazans text messages, and making landline phone calls as well, warning them to not to allow themselves to become “human shields” for terrorists whom the IDF will eventually eliminate.

The technology to overpower radio, television and cellphone signals is actually very simple, said David Maman, CTO and cofounder of the database security firm GreenSQL. When it comes to overpowering a broadcast, it’s basically a matter of who can outshout whom.

“All I need is a transmitter that outclasses the one used by the broadcaster I am targeting,” he told The Times of Israel. “A transmitter with higher wattage output, higher voltage, and wider range can ‘outshout’ a broadcast using the same frequency.”

Radio broadcasts, in particular, are easy to overpower, Maman said. “This was actually quite common just a few years ago in Israel, when we would hear reports about pirate radio stations that were using the same frequencies that pilots coming into Ben-Gurion Airport were using, interfering with the transmissions.”

It’s still common today; drivers in the West Bank and neighborhoods of Jerusalem often find that the broadcasts from officially licensed Israeli radio stations are “outshouted” by Arabic-language broadcasts as they pass near Arab villages. Although the Oslo Accords provided for regulation of Israeli and Palestinian radio broadcasts, with frequencies to be utilized in a way that did not interfere with broadcasts from either side, this has never been enforced, Israeli officials said.

“You could buy the equipment to do this from a Radio Shack, and put yourself on the air on any frequency, even one already in use,” said Maman. “If your transmitter is superior to the one used by the party already using the same frequency, or if your transmitter is in an area far enough from the stronger transmitter so that your signal is stronger than theirs, your transmission will be the one that gets heard.” Although it is illegal for individuals to broadcast over licensed frequencies, “obviously the IDF has the authority and resources to do this.”

Radio signals cannot be encrypted, said Maman — and neither can cellphone signals on public networks (which are essentially radio frequencies as well), so breaking into either is easy for those who know how.

The same principle applies to television broadcasts, although, unlike terrestrial radio signals, it’s a bit more difficult to “crack” the digital signals used by those technologies. Hamas, like nearly everyone else in the Middle East, now uses satellite to broadcast its TV channels.

“For encrypted digital satellite broadcasts, such as those from YES, it’s very difficult to break into the signal, unless you have the security key to unscramble the broadcast.” However, that’s not the case for Hamas’s TV stations; in order to ensure that as many people can see its programs as possible, Hamas uses unencrypted free to air satellite signals. All the IDF would have to do, said Maman, is aim its broadcast at the same digital channel Hamas is using, again outclassing their broadcast.

“It’s a matter of who can shout the loudest,” said Maman.