Investing.com -- Robotics and space stocks could be among the most vulnerable in any market downturn, KB Securities has warned, drawing parallels between today's thematic investment frenzy and the final stages of the U.S. dot-com bubble.

In a note to clients, analyst Euntaek Lee argued that the dot-com collapse unfolded in a sequence of stock collapses rather than a simultaneous crash, a pattern it believes offers a roadmap for identifying today's most at-risk sectors.

The first stocks to fall during the dot-com era were those with valuations "most dependent on future expectations rather than near-term cash flows," such as AOL, Yahoo and Qualcomm, which began declining as early as January 2000, a full quarter before the Nasdaq peaked.

The second wave hit companies tied to excessive capital expenditure expectations.

KB Securities said today's market echoes that dynamic, noting that "certain thematic sectors such as power, robotics and space may fall into this category" of stocks with weak earnings and far-out profitability.

The bank pointed to May's market turbulence as an early warning signal, observing that during a period of pressure tied to the Samsung Electronics labor strike, "stock volatility was highest not for Samsung Electronics but rather thematic stocks such as robotics and space."

By contrast, KB Securities argued semiconductors are better positioned to weather any downturn.

"Companies with actual earnings delivery are likely to be the last survivors of the current market surge," Lee wrote, adding that semiconductor companies "may be the most likely candidates."