Coded messages. Landline phones. Pagers. Following the killing of senior commanders in targeted Israeli airstrikes, the Iran-backed Lebanese militant group, Hezbollah, has been using some low-tech strategies to try to evade its foe's sophisticated surveillance technology, informed sources told Reuters.

It has also been using its own tech – drones – to study and attack Israel's intelligence gathering capabilities in what Hezbollah's leader, Sayyed Hassan Nasrallah, has described as a strategy of "blinding" Israel.

The sides have been trading fire since Hezbollah's Palestinian ally in the Gaza Strip, Hamas, went to war with Israel in October. While the fighting on Lebanon's southern border has remained relatively contained, stepped-up attacks in recent weeks have intensified concern it could spiral into a full-scale war.

Tens of thousands of people have fled both sides of the border. Israeli strikes have killed more than 330 Hezbollah fighters and around 90 civilians in Lebanon, according to Reuters tallies. Israel says attacks from Lebanon have killed 21 soldiers and 10 civilians.

Many of Hezbollah's casualties were killed while participating in the near-daily hostilities, including launching rockets and explosive drones into northern Israel.

Hezbollah has also confirmed the deaths of more than 20 operatives - including three top commanders, members of its elite Radwan special forces unit and intelligence operatives - in targeted strikes away from the frontlines.

Israel's military said it was responding to an unprovoked attack from Hezbollah, which began firing at Israeli targets the day after Hamas attacked Israel on Oct. 7. The Israel Defense Forces (IDF) said in a statement to Reuters that they were striking military targets and taking "feasible precautions in order to mitigate harm to civilians."

"The success of these efforts hinges on the IDF's ability to gather thorough and precise intelligence on Hezbollah's forces, its leaders, the organization's terrorist infrastructure, their whereabouts and operations," the statement said.

The IDF did not answer questions about its intelligence gathering and Hezbollah's countermeasures, citing "reasons of intelligence security".

As domestic pressure builds in Israel over Hezbollah's barrages, the IDF has highlighted its ability to hit the group's operatives across the border.

On a tour of Israel’s Northern Command, Defence Minister Yoav Gallant pointed to pictures of what he said were slain Hezbollah commanders and said 320 “terrorists” had been killed as of May 29, including senior operatives.

Electronic surveillance technology plays a vital role in these strikes. The IDF has said it has security cameras and remote sensing systems trained on areas where Hezbollah operates, and it regularly sends surveillance drones over the border to spy on its adversary.

Israel's electronic eavesdropping - including hacking into cell phones and computers - is also widely regarded as among the world's most sophisticated.

Hezbollah has learned from its losses and adapted its tactics in response, six sources familiar with the group’s operations told Reuters, speaking on condition of anonymity to discuss sensitive security matters.

Cell phones, which can be used to track a user's location, have been banned from the battlefield in favour of more old-fashioned communication means, including pagers and couriers who deliver verbal messages in person, two of the sources said.

Hezbollah has also been using a private, fixed-line telecommunications network dating back to the early 2000s, three sources said.

In case conversations are overheard, code words are used for weapons and meeting sites, according to another source familiar with the group's logistics. These are updated nearly daily and delivered to units via couriers, the source said.

"We're facing a battle in which information and technology are essential parts," said Qassem Kassir, a Lebanese analyst close to Hezbollah. "But when you face certain technological advances, you need to go back to the old methods - the phones, the in-person communications … whatever method allows you to circumvent the technology."

Hezbollah's media office said it had no comment on the sources' assertions.