Barcelona's interest is closely tied to the uncertain future of Jules Koundé, who has attracted offers from the Premier League this summer.
According to Spanish outlet Jijantes, Barcelona have been in touch with Porro's representatives to establish his contract situation at Tottenham and to gauge what a transfer might cost, with a right-back move still possible before the window shuts.
The interest follows Porro's standout performances at this year's World Cup, where president Joan Laporta and sporting director Deco were both said to have taken note of his displays for Spain.
Porro signed a new contract in mid-June that ties him to Spurs until 2031, with the option of a further year, and manager Roberto De Zerbi regards him as a key part of his system, praising his ability "to influence matches in both defensive and attacking situations" after the renewal was announced.
The 26-year-old scored one goal and made two assists in 34 Premier League appearances last season and has only grown in stature since, helping Spain win the World Cup this summer in one of the tournament's standout defensive performances, forming a productive partnership down the right with Barcelona's own Lamine Yamal.
Barcelona have separately been working to complete a permanent deal for João Cancelo, who spent the spring on loan at the club from Al-Hilal.
The Portugal international remains registered to the Saudi club for now, but Barcelona are expected to get the move over the line for a fee in the region of €10m, which would ease some of the pressure in defence regardless of how the Porro situation develops.
Tottenham moved to secure Porro's long-term future before the World Cup specifically to head off interest of this kind, and question marks over Jules Koundé's stay in Catalonia mean Barcelona's approach for now amounts to information-gathering rather than a concrete bid. Real Madrid have also been credited with past interest in Porro, though sources in Spain suggest Los Blancos are not currently in the market for a right-back, having already strengthened elsewhere in defence this summer.