what are technique for negative seo ?

Negative SEo is the act od using Back Hat SEO on other websites in order to get them penalized by Google.

• Hacked Site
• Profile Spam Links
• Comment Spam, Forum Spam Link
• Duplicate Content
• Fake & Duplicate Reviews
• Low Quality Backlink

5 Negative SEO Techniques That Could Hurt Your Website
Evil Backlinks
Evil Content Scraping
Evil Hacking
Evil Crawlers
Evil Reviews

Black Hat SEO Techniques -
1. Cloaking
2. Page Hijacking
3. Doorway pages
4. Link Firming
5. Keyword staffing

These are technique of negative seo

• Automatically generated content
• Participating in link schemes
• Creating pages with little or no original content
• Cloaking
• Sneaky redirects
• Hidden text or links
• Doorway pages
• Scraped content
• Participating in affiliate programs without adding sufficient value
• Loading pages with irrelevant keywords
• Creating pages with malicious behavior, such as phishing or installing viruses, trojans, or other badware
• Abusing rich snippets markup
• Sending automated queries to Google

Simply put, Negative SEO is the act of using Black Hat SEO on other websites in order to get them penalized by Google. Negative SEO can also include reducing the effectiveness of a website's SEO properties by disabling or altering them.
What is Negative SEO in a nutshell.
Negative SEO in a nutshell.
Dealing with Negative SEO can be quite tricky since some of them is out of your control, like pointing bad links to your site. Another thing is, they are also a bit hard to detect. Unlike some hacking practices that aims to deface or simply take down a website, a Negative SEO attack doesn't affect a website's look and feel.
Instead, the effects are only apparent once your website takes a dip in search ranking and incoming traffic.
But Why Would Anyone Commit A Negative SEO Attack?
Similar to hackers, people who do Negative SEO attacks might do it for various reasons. It can be intentional, such as sabotaging a competitor's website, extortion or simply for fun.
And believe it or not, an unintentional Negative SEO attack can also happen. There are cases where family members, employees or even hired SEO agencies deliberately do obsolete Black Hat practices on behalf of the owner thinking it will help their website ranking.

and there are 5 technique for negative seo could be hurt your site
+ Evil Backlinks
+ Evil Content Scraping
+Evil Hacking
+Evil Crawlers
+Evil Reviews

Sometimes Negative SEO is also used for competitors website in which will ruin their reputation in the search engine.