China is tightening its border rules from mid-September, and it's bad news for anyone traveling there with company technology or working for a firm Beijing dislikes.

• New rules let Chinese authorities block people from leaving over vague charges like handling "sensitive technology" or working for a hostile company.
• Chip and IC design engineers on business trips are the most exposed — a laptop or phone holding process or research data can trigger a search or a travel ban.
• Even local border officials can impose exit bans on their own, so the risk is unpredictable.
• Many multinationals now order staff to carry clean, dedicated phones and laptops to China and never bring their normal work devices.
• Related laws on ethnic unity and internet content are being pushed at the same time, a sign of heavy pressure inside China to keep control.

Outlook: Taiwan's security agencies are preparing tougher travel guidance for business trips to China, and companies are likely to cut non-essential travel there.