You see them everywhere from the moment you arrive at the airport. They are the porters and floorsweepers, the hotel personnel, the road construction crews, the carpenters and masons of the booming building trade and the semiskilled and even highly skilled workers of Saudi Arabia's new advanced industries.

Officially numbering 1.7 million and making up 43 percent of the entire labor force, the omnipresent mass of foreign laborers -- Filipinos, Pakistanis, Indians, Koreans, Taiwanese, non-Saudi Arabs and Westerners -- has become a national preoccupation and a recognized security risk with which the government is grappling with an increasing sense of urgency.

The entire Saudi development strategy is geared to limiting the tide of foreigners flooding the country, and the government is revamping its internal security system in the wake of the Mecca "accident," which involved a number of outside Moslem fanatics as well as Saudis in the bloody seizure of Islam's holiest site in November 1979. Twenty-two of the 63 subsequently beheaded for mounting the attack were non-Saudi Arabs.

A decree issued last August restricting the influx of foreign workers' families has been applied with such rigor that even high-level Western management personnel are complaining bitterly about the problem of obtaining visas for wives and children, and sometimes even themselves.

Preparations for the Islamic Conference summit in Taif in late January served as the occasion for a thorough security check on foreigners, particularly those living here and in Taif and Mecca, that reportedly turned up tens of thousands of illegal aliens. Exactly how many were deported in unclear but one figure circulating in Western diplomatic circles is 60,000.

French security experts working with the Interior Ministry are said to be advising the Saudis to set up a system of identity cards as part of improved surveillance of foreigners that also would include a closer check on their departure once the job for which they were hired is finished.

The dimensions of the foreign presence are probably even greater than the large official number of outside laborers might suggest. The 1 million or more Yemenis working or living in the kingdom enjoy a special status that allows them to cross the border at will, thus making it difficult for the government to keep tabs on their exact number.

Thus, unofficial estimates of the total foreign population put the figure at 2 million or more compared to a Saudi population of somewhere around 5 million, or at least 40 percent. Whatever the figure, the government is only too well aware that even by its own figures the share of Saudis in the total work force has dropped dramatically from 72 to 57 percent in the past five years.

One measure of national sensitivity to the problem is the enormous publicity given in practically every development story in the local press these days to the number of Saudi nationals applying for jobs in the kingdom's new industrial plants. Anything suggesting that Saudis may be capable of running them, or at least of making up the majority of workers, is big and obviously welcome news.

Despite the vast numbers of foreign workers, Western residents say they generally respect the rigid Saudi social code -- which forbids alcohol, bars and even movie houses -- and that crime is no problem. "It's one of the safest places I've been in my life," said one Western diplomat. "When the police stop you they are not looking for a bomb or a gun but a bottle of booze or girlie magazine."

Saudi officials who are involved in the kingdom's industrial great leap forward, such as Hisham Nazer, the economic planning minister, heatedly defend a decision taken 11 years ago at the beginning of the first five-year plan to push all-out for rapid industrial development that assured a heavy dependence on foreign labor.

"I'm not worried about it at all," Nazer said in an interview. "Maybe I'm one of the very few. They [foreigners] have contributed a great deal to Saudi development. The positive aspects outweigh the negative ones.

"Many felt our development was too fast," he continued, "because it was built with foreign manpower. But who wanted to wait 20 years to depend only on Saudi labor?"

But Nazer says there is now a de facto freeze on foreign labor and explains that the new third five-year plan is deliberately aimed at reducing the emphasis on infrastructure, which required the huge influx of foreign labor, and stressing instead the building of capital-intensive, low-manpower industries manned primarily by Saudi nationals.

He cited as an example the two huge industrial cities rising from the sand in Jubail on the Persian Gulf and Yanbu on the Red Sea, whose nine petrochemical, other oil-based plants and steel complexes, he said, will require only 8,000 persons to run them. When these plants begin to operate in the mid-1980s, Saudi nationals are expected to account initially for 65 to 70 percent of the labor force.

Another example Nazer gave of labor-intensive industry was a $12 billion gas-gathering system being erected in the eastern oil fields that needs only 500 experts to run it.

The government is placing an enormous emphasis on manpower training for Saudis with the objective, as stated in the third plan, "of reducing foreign manpower by Saudis to the maximum possible extent." Of the whopping $237 billion investment scheduled during the next five years, nearly 19 percent is earmarked for human development.

In answer to foreign skeptics of the Saudi assumption that there will eventually be enough skilled Saudis to run the economy. Nazer points to the giant Arabian American Oil Co., or Aramco, the country's single biggest industry, which he said is 80 percent Saudi in its staff.

Figures published in the Saudi press indicate that only slightly more than half of Aramco's 46,870 employes were Saudi in 1980, with Saudis holding 46 percent of its supervisory positions.

A close reading of the third development plan also suggests the freeze on hiring foreign labor mentioned by Nazer may in fact be more theoretical than real and involve primarily a shift away from manual to more skilled workers.

While the plan foresees 65,000 foreign laborers leaving the country by 1985, primarily in the construction industry, it also estimates that there will be an additional need for 74,000 foreigners, giving a net growth of 9,000. But, it argues this will be only a fraction of the 155,000 new jobs created during the five-year period.