The number of Wall Street cheats illegally using inside information appears to be climbing pretty rapidly. This is evident from the stepped-up number of stock trading investigations by the various securities and regulatory agencies, according to a brokerage compliance source with strong regulatory ties. Such trading probes, he estimates, are running about 10% to 15% ahead of last year’s levels.

Noteworthy in this respect, I’m told, are the investigations of the securities — both stocks and options — of companies caught up in the current mergers and acquisitions boom, the kind of Wall Street action that lends itself to making quick killings through the abuse of non-public information. The names of overseas investors are said to be popping up with growing frequency in such probes, as are hedge funds.

The threat of such penalties as jail time and hefty fines for illegally trading on inside information is apparently having little effect on the number of unethical investors who think they can beat the system.

An indication of this can be found in the five new independent trading investigations begun by the Securities and Exchange Commission and the market regulation arm of the New York Stock Exchange involving sizable M&A-related transactions, informed regulatory sources tell me. Among them are companies that have received both friendly and unsolicited bids.

“The bad guys out there seem to be forgetting about the computers. It’s no longer a game of ‘Thieves Anonymous,'” one regulatory contact said.

The five cases mentioned all involve multibillion-dollar deals that in total add up to $66.9 billion worth of transactions. The companies are:

• MedImmune, a leading biotech company that makes a nasal spray flu vaccine, FluMist, is being investigated by the SEC. MedImmune received a $15.2 billion offer from a Britainbased pharmaceuticals manufacturer AstraZenaca, just after the company engaged Goldman Sachs to put it up for sale. Med-Immune took the action in response to pressure from activist investor Carl Icahn, who had acquired a stake in the company.

• Harrah’s Entertainment, the big casino and resort operator, which got a $17.1 billion buyout offer from Apollo Management and the Texas Pacific Group. The SEC is also conducting this trading investigation.

• Alcan Inc., one of the world’s largest aluminum producers. Based in Canada, it received an unsolicited $27 billion offer from rival Alcoa. The NYSE is handling this probe.

• Florida East Coast Industries, the owner of the Florida East Coast Railway, which hauls crushed stone, intermodal motor vehicle containers, and other goods. Funds managed by the Fortress Investment Group are buying the company for $3.5 billion. The Big Board is also conducting this trade.

• Armor Holdings, a diversified manufacturer of branded products, including vehicle armor systems, for the military, law enforcement, and personnel safety markets, has agreed to be acquired for $4.1 billion by BAE Systems, a wholly owned subsidiary of BAE Systems PLC, a global company engaged in the development, delivery, and support of advanced defenses and aerospace systems. This investigation is under the Big Board’s jurisdiction, as well.

Aside from these five probes, two additional trading investigations were recently commenced, one of which is focused on Limited Brands, the retailing apparel and accessories giant and owner of the Victoria’s Secret chain. The other is 3Com Corp., which sells networking hardware and software equipment. These two probes are being conducted by the NYSE and the SEC, respectively.

As part of their investigations, both the Big Board and the SEC have recently fired off requests to the brokerage community requesting the names of clients both here and abroad who have traded in these various securities in specified time periods.

Asked about these investigations, a spokesman for the SEC declined comment; a spokeswoman for the NYSE told me, “We’re not going to comment on investigations.”

dandordan@aol.com