AMNA NAWAZ: Espionage in wartime is as old as war itself, and the protection of vital information a key component of an effective military, but it may be time to update the old adage loose lips sink ships for the digital age and the Russian invasion of Ukraine.

As special correspondent Jack Hewson shows us, Ukrainians are using social and news media posts to cull information about their Russian adversaries.

JACK HEWSON: Weapon silo burns deep behind Russian lines at the base of the Pyatnashka Brigade.

This is one of many Ukrainian strikes in the summer of last year, most likely perpetrated using HIMARS, a guided rocket system supplied by the U.S., a technology that, at the time, helped turn the tide of the war in Ukraine's favor.

But the targeting for this attack started out far from the front line here at this anonymous office block.

Where are we?

ARTEM STAROSIEK, CEO, Molfar: Here, the office of the Molfar.

JACK HEWSON: Molfar are a corporate investigations company that is using open-source Internet investigations, or OSINT, to target Russian forces.

In turn, the Ukrainian military is then using this intelligence to kill them.

Molfar CEO Artem Starosiek: ARTEM STAROSIEK: We have a team of our analysts, like in-house employees of Molfar, and they have volunteers who are just helping us.

And we have like a system where we pass all the information from Telegram, from contacts, from all the social networks which are used by Russians.

JACK HEWSON: It's using online posts like these that Molfar was able to locate the aforementioned Pyatnashka Brigade.

This video shows the brigade's anniversary celebration posted on its Telegram channel.

Here, the unit commander, Akra Avidsba (ph), is congratulated by Denis Pushilin, in the Russian backed head of the so-called Donetsk People's Republic.

As the commander is presented with three civilian drones, it's clear that the event is being held in a workshop with characteristic garage doors.

In another local media interview, the dateline states the location is the city of Donetsk.

A passing truck gives away the existence of an adjacent main road.

And later we see that a secondary white and gray building with makeshift wooden shelters in front of it sits by the workshop.

Another video shot at a different time shows Ukrainian prisoners of war sat at those same wooden shelters being given food.

In the background, you see the workshop that hosted the anniversary event, an armored fighting vehicle and a civilian structure with a spire adjacent to the facility.

Looking the other way, behind the commander is a brick building obscuring a blue and white hangar.

More perusing of a local reporter's Telegram channel yielded clearer shots of the white and gray building, the abandoned brick structure, and the blue and white hanger.

In addition are distant power lines also observed in several other photos and videos seen by PBS.

This gave enough clues to understand the base layout, according to Molfar analyst Oleksandr.

OLEKSANDR, Molfar (through translator): We analyzed these videos and made a map of the approximate locations of these buildings and how they are located in relation to one another, with help of Google Maps and Google Google Street View.

Knowing that the deployment is in Donetsk - - the fighters themselves have indicated this -- we established specific buildings, places of deployment.

JACK HEWSON: Finding the exact location was made easier by this video of a tank leaving the site.

The local street signs suggested the general area to be Eastern Donetsk.

With the leads they had, Molfar claimed it took approximately two-and-a-half-hours to find the base.

On Google Street View shot from the Donetsk Bypass in 2011, you can see the workshop here, the building with a red spire, and the headquarters prior to the addition of its white and gray cladding.

From another angle, you can see the blue and white hangar and power lines in the background.

They had a match and a pinpoint location on Google Maps.

One month after they passed their target report to Ukrainian intelligence, the site was struck on August 22, according to local media reports and this drone footage.

Molfar did not know how many troops perished or if the Ukrainian prisoners of war were killed in the strike.

Most people familiar with the term OSINT think of Bellingcat or other citizen journalist organizations investigating military or criminal wrongdoing.

But what is new in Ukraine is how these techniques have been reverse-engineered to kill enemy forces and destroy enemy hardware, something I put to Starosiek.

ARTEM STAROSIEK: It's strange, because when we found in, like, location of Russian there, will be killed in the future.

And it's strange to use this.

But, from other side, there is a war.

We didn't started this war.

And we're, like, defending ourselves.

So I'm not feel bad from moral side.

And I'm happy from this and I'm happy when our digital work gives results on the real battlefield.

JACK HEWSON: But if Russian social media posts are helping the Ukrainian war effort, would it be better to keep quiet?

If anything, this creates more risks for you through telling me.

Why are you telling me this?

ARTEM STAROSIEK: I think first goal is to show Russians that we are not afraid of them, and they will get a lot of pain here.

JACK HEWSON: According to Molfar, the Russian Ministry of Defense has now cracked down on Russian journalists' access to the front line and to sensitive sites.

It means they get less information from these sources, but they claim still to get some actionable intelligence from Russian media.

Instead, their focus has shifted to the social media posts and posts on Telegram by Russian soldiers and the volunteers that support them.

The weaponization of open-source Internet investigations has permanently changed modern warfare.

For the "PBS NewsHour," I'm Jack Hewson in Ukraine.